The workshop having infinite # of upgrades per unit will honestly break the game and severely disadvantage the smaller players in battle.
Here is a scenario:
Player 1 has a top score of 50m
Player 2 has a top score of 5m
Player 1 attacks player 2.
Player 2 has not had the same amount of time and resources to invest in workshop upgrades as player 1.
Player 1 has invested millions into upgrading their units and can easily trounce the low-level player.
My solution:
Raise the workshop research cap from +3 armor and +3 attack to +25 armor and +25 attack.
Add new battlefield sizes to the sea and land fights. The size can be determined on the number of units the defender has above the town capacity.
If this is implemented into the game as planned, low level players will quit playing the game because they will be easily bullied.