It seems like there are a lot of mod and total conversion ideas in here. On that note, there are a lot of posts in here, I tried to read them as I could.
Not sure if the newer ideas are being considered, but I have come up with some (which may have been posted similarly already, I am sorry if they are). If I have accidentally copied your idea, at least that means you have my support for the idea! Anyways, my ideas:
1.Angel of Rockets: Only able to use Rocket and Missile Launchers, ammo will obviously be limited so technique is required to succeed, but game may be easier on higher difficulties since mancubi and remnants will appear earlier to drop rockets. Difficulty: Hard.
2.Angel of Hotfoot: "You've always had some hot, sweaty feet. These military boots don't seem to help much either. Seems like your sweat, combined with the evils of Hell, leaves the floor tarnished." Each step has a 1%-3% chance of creating lava (maybe acid instead) where you just moved from, possibly even on doors, water, or acid. Dodging back and forth will be more risky. Environmental suits will be more important in some instances. Difficulty: Medium. (estimate)
3.Angel of 100 tweak: Same concept as before, but now every 10th level is an arena with a special boss, probably human, wielding one of the advanced weapons or uniques. Possibly make it so these enemies are the only way to get uniques in the challenge. Scale the types of uniques to the difficulty (would BFG guys be overkill even for N! ?). This adjustment would make the Challenge more of a challenge fitting to the name Blade, instead of just 100 levels of regular DoomRL levels.
4.Angel of Badassery: "You were always the tough guy. Never wore a coat, even in the coldest bitter winter. You had to look cool. Now, you won't give in to the need for armor or boots" (or even a backpack, possibly). [optional balancing feature: You start off with one level of Tough As Nails inherent, but it doesn't get counted on your trait selection.] Difficulty: Very Hard