Other than that basic units should have the same limit as the other unit types (3) this would stop all zergs.
excluding basic footmans imo - that should be balanced and balanced until goes into Zen status
edit
but there should be limit build for 250/400 brackets and not in company management
the TOU gives stability also to your opponent plans, not only yours. With my wolven i can plan all my pursuit movements vs ram as i generally always hit them.
I like to think that my plans are better than enemy plans
Maybe you always Hit Ram units - but they can handle that... its still better than Swordsmans 20% to parry and 80% to die quicker than skeleton ;p
When i play with War Lions or Gargoyles i really can't rely on thein Parry if i want to have Win ratio better than 50:50
But both are solid offensive units... while Swordsmans are defenders only - that i can't rely on