interesting game, the different conditions you place certainly make for some interesting things you have to work around. can't wait to see where you go with this.
btw: 5 starred level 6. for those with trouble (as I see in reviews) how I did it:
7 upgraded captains + 3 upgraded high priests.
anything not literally required to buy those 10 units, I didn't get (even a watchtower!)
hope that helps.