Everything I don't address I am in agreement with as you proposed.
I think a nice change could be having 25 of each badge for a nice rounded number, instead of 26. This includes Angelic Badges.
26 is a weird number but I would be fine either way, I certainly won't miss annoying badges like the Scavenger Platinum/Diamond badges if they were removed. Alternatively, we bump them up to 30 if people would rather not see any content removed, shouldn't be too hard to think up of a few more badge ideas for each tier?
Apostle in-game ranking requires 50 JC kills, which is fairly tedious and the point tends to get made fairly early on. It could be left as is to encourage it as a long-term goal, but I think in terms of grinding for rankings, 25 would be fine. I'm open to this being rejected though.
I don't think this one is bad, having a few more XP rankings to build up more gradually to it would be better I think. I also got stuck before reaching Cyberdemon for a long time because just killing 100 Cyberdemons was a big jump from what Archvile rank required, and I didn't want to go farm Cyberdemons in A666 just to advance the XP rank faster (in fact with your proposal, I would have reached the requirement for Apostle rank faster than I did with the Cyberdemon rank). Also maybe put the JC kill requirements for a different rank and save Apostle rank for actually getting Apostle kills?
Cyberdemon Cross - Enter and exit a Cyberdemon complex alive.
First thing, I would extend this to covering any boss-only level (maybe including Agony Elemental and Lava Elemental caves if it's possible to program it that way, as well as an Angel of Death complex if that gets added alongside the AoD getting added to A100/666). Would require less luck than finding a very specific level type that's very rare, and the other boss-only levels could be even harder (for example I think a Shambler level will usually be harder, and Agony Elemental caves are hell for most builds that don't have a Nano Super Shotgun or Biggest Fucking Gun handy). Secondly, it should require the player to clear the level to get this medal, to make it more of an achievement and so you can't just immediately homing phase out to get this medal.
Scavenger Medal - Create 15 or more assemblies (maybe require them to all be different too?).
I would agree with making it require 15 different assemblies. Also name it "Technician Medal", to avoid any confusion with the Scavenger series of badges that have nothing to do with assemblies.
Purity Medal - Kill JC on Angel of Purity.
Shottyman Medal - Win Angel of Shotgunnery with 100% kills.
I would rather have new medals that could be more generically applied instead of being challenge-locked (unless it's for A100 as I mentioned in my initial suggestions post). I also don't like these suggestions; I'm assuming the Lava Element still works in AoP (because otherwise how could you get that medal), in which case it's really not much different from getting a normal full win (you could no longer rely on a random Invuln spawning, but most people going for a full win just get the Lava Element), and with the latter suggestion, there really isn't anything particularly special nor challenging about it, while it would be inconsistent to have that but not an equivalent medal for AoMr.
UAC Cross - Kill 10,000 or more enemies.
I would change this to 2500 kills, so that it's still obtainable in A100 with sufficient reasonable effort (would require some farming on HNTR, killing near 100% on HMP, and still killing most things on UV and N!, bump it to 3000 kills to keep it more exclusive to UV/N!). I'm not keen on a medal that is essentially A666-exclusive.
Brick Silver Badge - This challenge is fairly annoying, but I personally like it and wanted to mention not changing it.
I'm fine with it staying, but would rather it become a Gold badge, since it requires a lot more concentrated effort to get than other Silvers and most Golds. You could have it swap places with Scavenger Gold (which is ridiculously trivial for a Gold), and in effect remove current Scavenger Silver (why does this one even exist).
I would say for going from 26 to 25, remove Armorer Gold Badge (other associated changes below).
Change Armorer Platinum Badge to requiring finding all exotics/uniques. Finding 1,000 either devolves into spamming Angel of Overconfidence games where you drop your starting gear, pick them up, then repeat, or alternatively with playing properly, finding duplicates of exotics and uniques within the same game still only counts as 1, so this is a massive grind of games to get to 1,000. Both methods are pretty unappealing. If for canonical reasons that having "Armorer X Badge" for each type except for Gold, we could change "Armorer Platinum/Diamond Badge" to something like Collector Platinum Badge and Collector Diamond Badge.
I think it would be weird for the Armorer series to skip having a Gold badge and think they're mostly fine as is, with maybe bumping down what Armorer Platinum requires. However, there wouldn't really be a better candidate among the current Golds to remove if my proposal of swapping the tier of Brick Silver and Scavenger Gold is done (maybe Longinus Gold, because that's trivial unless you change it to require no Brute), so I would be ok with cutting Armorer Gold and going with your rename idea of "Collector Platinum/Diamond".
Berserker Platinum Badge - This badge is fairly similar to Gargulec Cross. Maybe change it to no kill count required, but on Nightmare difficulty?
I rather remove the kill requirement and keep it on UV difficulty to differentiate it more from Gargulec Cross. The Berserker series shouldn't skip UV difficulty, and changing Berserker Platinum to require Nightmare would also make the Gargulec Cross essentially require its own dedicated run to get (can't get it alongside the lower tier Berserker badges, and trying to get it on Nightmare is lunacy).
For going from 26 to 25, I would say remove Scavenger Platinum Badge since it's a bit silly and the optimal way to earn this is not so much by "luck", but by spamming Azrael's Scythe's Whisper of Death.
For going from 26 to 25, I would say remove Scavenger Diamond Badge for the same reasons as mentioned above.
I alluded to earlier that I would like these badges be changed even if my proposal of swapping Cathedral and Vaults goes through (which would invalidate the Whisper of Death cheese), so these would definitely be my pick to go if we're rounding out the badges to 25 each. Purely luck-based badges are very annoying, and their presence just encourages people to save scum to get them out of the way (though if my proposal to make Vaults harder on harder difficulties also goes through, getting Scavenger Diamond could be tricky to get even if you do get the luck to phase into the central vault, and it we're keeping Brick Silver, Scavenger Platinum/Diamond isn't out of place).
Arena Diamond Badge - Change this to Ultra-Violence as this badge is significantly harder than every other Diamond Badge. This is the only one Papilio never earned and he seemingly gave up on it, despite earning most if not all of the other purely.
My stance on this hinges on the proposal to give Hell's Arena different enemy loadouts based on the challenge. If that proposal goes through and AoB appropriately gets an easier Hell's Arena, then this badge can stay as is. If that proposal cannot be done however, then yes bump it down to UV.
Hunter Angelic Badge - Complete Archangel of Darkness on Nightmare (assuming this gets added).
Agree with this, but in the event that Archangel of Darkness isn't added but this badge is, it could alternatively be beating Angel of Darkness on Nightmare as a Conqueror?
Demonic Angelic Badge - This is basically an open slot for a new idea lol. Maybe Archangel of 666 on Ultra-Violence with 100% kills?
I would like the idea to reward people crazy enough to get 100% kills in A666 on UV, but I also don't want to have to force such a massive grind requirement on anyone. That would also not adhere to the theme of the Demonic series all requiring N! difficulty. Maybe build off of Demonic Diamond and have it be 100% kills with Untouchable Medal in a standard N! game? Or if that's still unobtainable, 100% kills + Untouchable Badge in standard N!?
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I also got some more suggestions of my own:
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In mortems, highlight badges with colors of their respective tiersJust a nice QoL thing to make the badges pop out more when looking over your mortem at the end and to give that extra dopamine rush when getting the harder badges. Could also have obtained badges highlighted in their respective colors in the Player Info's badge collection screens. Could give medals their own unique highlight too, but I don't know what coloring for them.
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Change Gatekeeper Gold to getting past Anomaly without damage on at least HNTR or HMP. Additionally swap Gatekeeper Platinum and DiamondCurrent Gatekeeper Gold is very trivial, with only Scavenger and Longinus being able to compete with being the easiest Gold, while it is also basically redundant with Cyberdemon's Head (the only way you won't always get both simultaneously is if you play ITYTD). My suggestion to keep it focused on Anomaly with a harder difficulty would be a much more appropriate Gold-level challenge and a more natural progression from Gatekeeper Silver, while the fact Anomaly completely lacks the ambush on ITYTD makes avoiding damage a much different challenge on harder difficulties. As for my second suggestion, I would say current Gatekeeper Platinum is more imposing than Gatekeeper Diamond, when the Cyber is still practically free to no damage on UV as long as you got Dodgemaster, leaving getting past Anomaly as the main stumbling block (and then just not dying until you reach Cybie, which isn't going to be that much harder if you're good enough to get to Deimos on UV). Anomaly also becomes
much harder on N! with the addition of nightmare enemies. If you think it would be weird to go from having the additional damageless Babel requirement to not having it, then just have both Gatekeeper Platinum and Diamond require it on their respective difficulties.
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Change Hunter Platinum to completing Angel of Darkness on UV with 75% kills (or any other reasonable kill percent)I mentioned before that I don't like the idea of a badge series skipping UV, and currently the Hunter series does that. It additionally doesn't make much sense, as going from HMP to UV in AoD would be a big jump in difficulty, whereas current Hunter Diamond isn't really that much more difficult than Hunter Platinum. I haven't looked through the mortems, but I would assume the vast majority of players who got both Hunter Platinum and Diamond knocked both of them out at once (all Hunter Diamond really requires beyond Hunter Platinum is saving a Homing Phase for Mortuary/Limbo, and maybe having one for Phobos Lab/Military Base and Halls of Carnage). This change should be a more natural progression of the Hunter badges.
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Make the Apostle possibly challenging?For a super secret final boss, the Apostle is a huge disappointment. Ignoring that he is just a super Archvile, he does have some qualities that could be threatening; a 40 damage plasma attack with a huge explosion radius is actually pretty damn scary even if you're berserked, when you're stuck in the horribly slow Berserker Armor that has no plasma resistance. He also teleports around and regenerates. But you get in once, you just hit him two-four times and then he dies possibly before he could even retaliate. I have a couple suggestions that could make the Apostle possibly come somewhat close to living up to its status:
1: Increase the Apostle's HP to 500
2: Have the Apostle immediately teleport whenever it is hit
He has 30 armor sure, but when you're berserked with the Dragonslayer and likely have several levels of Brute, that 30 protection ain't making that much of a difference in surviving longer than Carmack and the Mastermind (in fact on average, they are surviving one to two more hits than the Apostle does against a berserked Dragonslayer even with no Brute). Additionally, have him immediately teleport away when hit, so that the player can't just get in once and mash click to win. This would make his health regeneration matter, and the enemies he revive will become a bigger problem with wearing you down as you chase him around the map. These changes could admittedly make him annoying and drawn out, but an annoying drawn out fight is much more climatic than the complete disappointment he is now.