A double post, but continuing on from the last.....
Would a wall-breaching single-barrel shotgun alt-fire be worthwhile? Just as a broad thought?
Ingame: Shotgun alt-fire. Costs 5 shells, takes 5(?) seconds fire time and has a 70%(?) drop-off. High damage (damage=wall hit-points). May have to use plasma damage to destroy walls. Possibly destroying weapon (% or not?).
Explanation: I'm kind of assuming all shells in DoomRL have progressed to the point of being case-less ammunition. So therefore there is no base-collar on shells (or bullets for that matter, regardless of the original doom graphics), perhaps only priming charges to be pumped out/cleared. So this represents the marine "over-charging" a single-barrel shotty with five shells, ramming extra ones down the barrel, holding it against the wall and blasting them through. Maybe even just like a normal "over-charge" in that it destroys the weapon (or a percent chance to destroy it). A breach charge, slow to load/fire and of limited use with high drop-off. You can breach-charge a wall right next to you, but anything further is foolish. If damage was made to be just over wall hitpoints on average (small random modifier) but very high drop-off (and weapon destruction %) it would be useless for combat, but very useful out-of-combat. Too slow, too costly, but very handy to have. Just a good thing to make rockets as not your only wall breacher (I'm aware there's others). But it also stops early game deaths via acid pits/extreme monster room, etc.
I'd carry a shotgun through hell for corners/breaching. Otherwise, I'll just keep carrying my combat shotty for corners/scouting as always.........