I have a few suggestions maybe you can think over as you continue developing:
- 1st person possession. I know this would be a lot of work to implement, but imo it's one of the best features of the game. Possession runs where I try to fight most battles through grouping, exploring, and battling in 1st person rather than top down control of all units kept the game interesting and fresh for me for many years.
- How do the creatures interact with rooms/each other? It doesn't have to be anything major or affect gameplay, even small things can add a lot to a creatures personality.
- Keep the level system, learned abilities, and other pseudo RPG mechanics. But I doubt you would change that