A couple ideas:
1 - optional mode with a pursuer and enemy that SLOWLY follows you across the manor don't just teleport but actually paths to you and can't use the teleport gates either. (the exact model can be one of a few, such as ((posibly selectable with random option)) centaur, anthro lion, feral hellhound for example.) who after losing to just walks around with you in his balls.
2 - Some more room types
3 - non enemy obstacles (rooms without enemies but need to unlock path) stays unlocked unless rooms randomized. Can include some free open path that just need an interact which can be a lewd scene
4 - expanding on idea #3 maybe a variation of this with a mimic that will either trap you for a long period of time (ties into idea #1) or may eat a key.
5 - mimic pumpkins (both non-vore and vore variants) the non-vore tentacle fuck or blow the character.
6 - if this isn't already a thing not "golding" all the rooms leaves a surprise enemy at the ending door, and/or causes an alternant ending.
I'll probably think of more later.