originally i thought it would have been cool if instead the player had weapons that would become unstable as you took damage. weapons could break leaving the player in a vulnerable state, and with a default "pee shooter" weapon. essentially the weapons would double as a offensive + defensive thing giving you Armor (protection) and a way to attack, over time they would break down. if a weapon began to break down your shots would become stronger but harder to control and would bring you closer to a fragile state, when a weapon would finally lose its "armor points" it would get removed from your arsenal and you would have to survive.
Another idea i was thinking to do was make the enemies themselves be "unstable" by mutating into demon/cult member hybrids, a chance to mutate into other enemies upon death or randomly :V. didn't get to making demon variants of the enemies though :