This has huge potential...
The largest problem with the game is that there is no balance between units and the game becomes too easy. It should not be possible to just buy all archers and then mass deploy for the win every time. The high end units just seemed like glorified copies of the lower end units. Instead they should serve some special function.
Also, at the end of the round you get more and more money. After the first 3-4 rounds, the payout is so high that you get to buy hundreds of units and upgrade hundreds of times.... and then you mass again with even more powerful units and get even more money.
Bottom line - grant much less money at the end of each round, and try to find a way to make units work together so that its advantageous to buy several types, not just mass all the same kind.