This looks pretty promising. I would like these things in the mod as well:
1) Blending levels ALA Duke3D. You'd have to come up with a bizarre travel story in your mind (or give logic a hearty "fuck you") if you go between levels by falling through the sky and ending up in a closed room with unprovoked demons outside.
2) Weak helper humans and more numerous/smarter monsters. Yeah, I know the point is that you're a One Man Army, but still, there are humans out there that are still fighting or hiding. To counter the strength your helpers provide, there would either have to be more potential demon fodder or the demons would have to pick out the NPC's before you, unless you provoke them.
3) Wandering rifle/shotgun zombies. I did say they were potential fodder, but if you are sneaky enough, they become something worse: target practice. Also, they are seeking humans to eat, so don't expect them to stand still

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4) Less Cyberdemons/Spider Masterminds. Doom 2 turned them into monster of the week, so if there are only 1 or 2 in the whole mappack, and if they get steroid treatment (perhaps with LOS-style cutscenes thrown in), they will be re-promoted to boss status, and then some.
5) Non-linear and partially-destructible. Well, most wooden doors, windows, and cracked walls should be destructible, and perhaps 3Dfloors (if you wanna go that far) to give the buildings multiple stories.
6) Maintaining a Vanilla Doom level of (apparent) simplicity. Doesn't mean refraining from using ZDoom features

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