I think you should make a 2 play option like the monster gets money every time they do a loop and turret get money from killing them and they have separate money piles ik that would be very hard to put into the game its just something I would like to see and a random idea 

this is a good idea, but the monsters should get money when killed(low amount tho) to avoid towers just killing the monsters in a loop where they cant cross from the 3 cube(based on in-game experience)