Hello! Thanks for playing! I will go though both of these:
Multiplayer is probably a no go. I don't see myself doing it with Tamer.
The boss idea is in-line with the current plan for the game, while mini-bosses are in the cards, no work has actually been done towards them, so its a wait and see. The bosses every 10 floors are planned. Giant, Medusa, Skeleton King, Dragon, Kraken Queen, Alpha wolf, and a Frankenstein monster are all planned, not in any particular order though. The 1st will come out when the next lot of floors is released.
Thanks again for playing!