I think you already have thoughts of incoperating some of these... but just in case.
In MOM you had dungeons and or abandoned towers with item, treasures, artifact or trapped heroes. I would like to have that in the game. It adds to the randomness of the game and it adds a certain flavor to exploration.
I liked the idea that if you fail in your attempts you might wake a demon. (I believe I read that somewhere) Please keep that in the game. It's way cool.
The possibility to call forth creatures from the beyong to fight for you. That's also something that was fun.