So there are two other things that don't seem to be incorporated into DoomRL that exists in vanilla Doom, namely keys+locked doors and crushing ceilings.
Keys+locked doorsSo unlike
some other rogue-likes, DoomRL doesn't have the concept of a locked door. In vanilla doom, some doors/pillars were locked with one of the three "primary" keys/keycards (blue, yellow, red), where part of actually winning the game involved finding these keys to unlock the correct doors to progress. Now, I think it might be a little silly to generate levels where one needs to find the correct coloured keys to open up the right doors in DoomRL, but it would be an interesting mechanic to have doors that can be locked and unlocked with keys. Couple of reasons why this is a good idea: tactical advantage and giving more credence to "vaults" that are generated in the maps.
Having the ability to lock and unlock doors grant the advantage of being able to "lock out" the denizens, which can provides a boon (catch a breather from the rampaging demons) or a bane (surprise attack from locked up creatures). This will of course provide yet another resource for management in addition to healing, mods, ammunition and power-ups, which can add more diversity to the game.
Of course, with the ability to lock/unlock doors, it becomes more interesting if we have destructible and non-destructible doors/walls. Notice in vanilla Doom, doors are usually metal and can eat too much damage without getting blown to bits, as is the wall. DoomRL is a little divergent with doors blastable by shotguns and walls destroyed by rockets, but it would be interesting if we had different classes of materials for the door and walls. This will add on to the introduction of keys and provide more tactical diversity rather than just running and shooting blindly (okay, not so blindly).
Crushing CeilingsEarly players of vanilla Doom find that there are some levels where a moving ceiling will destroy them by crushing. Some of the more advanced players capitalise on that and use it to kill cretins. Adding crushing ceilings that do non-trivial amounts of damage in a fairly regular interval gives the player two important things: more tactical choices, and having a better sense of game time.
Ever been destroyed by a large Vile-pack because you didn't have enough firepower to take them on? Having crushing ceilings make it tactically more exciting because one can lure mobs to special "kill" zones to help them win. Note this is different from the kill lever that is already present -- kill levers need to be activated by hand, but crushing ceilings are completely regular in timing.
A sense of game timing is also a useful skill to have, since each discrete action taken by the player does not always correspond to the same amount of turns or in-game time. By pegging the crushing ceilings to a regular period in-game, players need to pay more attention to using it to their tactical advantage, which gives them a deeper appreciation of the underlying mechanics of the game, and that makes them better players.
Alright, I wrote a lot. Comments?