Now, I'm pretty new around here, and so my opinion of this game isn't as full as most of the vets around here, but even with my inexperience, I have to ask, what's the purpose of all these unlockables?
What I mean is, when you first start the game, all the challenges and the upper tiers of difficulty are locked until the player completes some arbitrary goals beforehand. These goals are both difficult and time consuming and I see no reason this feature in the first place.
Yes, I know these can be construed as rewards for playing the game well, but I'm of the philosophy that games shouldn't limit the player on what type of fun they want to have, that it's the game's job to provide the fun, and nothing else.
Now, I'm not bashing the 'rank' system entirely, I think it's very nice. It gives a little title to the players to make them feel good, and neatly falls into what I'd call a 'bragging rights reward'. It's aesthetic, it doesn't serve a practical purpose, but gives the player a reward for their hard work.
It's just that I don't think a player's rank should prohibit him from playing the game the way he wants to play.
Now, DoomRL is a roguelike, a genre I'm familiar with. Now, I'm of the opinion that a problem that a lot of roguelikes share is accessibility. New people have a hard time picking them up for any number of reasons. If someone that had never played a roguelike before were to download this game, and saw that most of it's challenges and difficulty were locked, and then upon doing more research (assuming he had the patience) to see what it takes to unlock them, and then found that he would have to do any number of difficult and time-consuming things, there is the very real possibility of him being turned off from the game, and just refusing to play it.
I really like DoomRL, and while I'm sure Mr. Kornel put thought into the system he's made, I think it would be for the best if the game gave all it's features to the player on startup, rather than expecting him to work for them.