The multiplayer / miniboss sounds like good ideas, but to be honest I'm not sure I will have enough energy to work on this...
I was especially interested for the miniboss. I had miniboss on floor 3 and 6 in my initial project but I had to get rid of them to focus on other features. Introducing more health-based boss would also add a reason to design weapons inflicting extra damages. Sounds good but I'm really close to release the project and I'm not sure I want to make that many change right now. Maybe for a sequel if the game is successful...
I plan to make a mac and maybe an android version. I would like them to be ready for 1.0