Technicians did get buffed in 0.9.9.8 by getting exclusive access to Whizkid 3 (so up to
seven mods on ranged weapons, four mods on armors/boots/melee weapons, and two mods on assemblies), which allows them to get better equipment than the other two classes can possibly have, and they can mod much more uniques than before too (this
wiki page covers what they can mod and to what extent). Their masteries were still largely lousy though aside from Scavenger (which also got buffed in 0.9.9.8 to be able to scavenge armors, boots, and melee weapons), but that is getting addressed in 0.9.9.9 (the exact changes aren't finalized yet, but so far; Malicious Blades deals a lot more damage with blades; Fireangel gets larger explosions and can make all non-shotgun ranged weapons explosive; SoG now deals +3 damage per level in exchange for only -10% firing speed, which completely reverses Sharpshooter's early game hell; Scavenger gets even more trait freedom than before; and with indirect buffs like Tough As Nails giving 10% energy resistances per level and direct buffs like ammo reduction on subsequent chainfire volleys, Entrenchment is actually good now instead of horribly awful).
Non-pistol Technicians still have a much harder early game than Scouts and Marines though, as the modding advantage and improved masteries don't manifest until later into the game, and near-instant item use and turning Computer Maps into Tracking Maps are more situationally useful than 10% faster speed on all actions or extra HP + inherent energy resistances, while the starting Technical Mod also doesn't really immediately help much unless you're a Pistol build or you get an early vault with a Combat Shotgun or good armor in it. I'm not sure how this can be addressed though; your proposed extra ammo capacity isn't necessarily a bad idea, but it wouldn't help the Technician's harder early game, the area they're struggling most in. I had an idea where they could get one "mulligan" per floor with activating levers, i.e. they can trip a dangerous lever once per floor without it activating (as it fits into their "hacking" theme and levers are more potentially useful early in the game where healing and armor recovery is more limited), but that ability is situational too and could be a hassle to program. Perhaps Technicians will just have to be accepted as the class that starts out weaker, but has stronger potential in the end than Scouts and Marines do with being able to obtain superior equipment.
Also since you brought up the Marine's energy resistances, I thought to let you know they are being nerfed to 10% in 0.9.9.9, as the 20% proved too strong since it still stacked with berserk and armors (which made Vampyre stupidly broken and Ammochain borderline broken too). But that 10% will still stack with all other resistances, including the aforementioned buffed TaN, and so they'll still be noticeably more tanky than the other classes (even without any armor nor TaN they'll still be able to take a couple extra hits, while the difference becomes very pronounced once they do get strong armor to stack that resistance on).