Hey! I've been playing this game for a while, and I have a few suggestions...
1. Maybe add some sort of summoner? Maybe something that spawns something else when it dies.
2. Please debuff Astronaut Path and Monster. Seriously.
3. I think a campaign would be beautiful. Maybe starting out with one or two hero slots and then over time you can hire more heroes, etc. Another thing to come along with this would be boss battles - could be very interesting, especially for an Auto-Battler.