A shame that units cannot be restricted, if a player wants to make armies composed of Triari there is nothing that can stop him. It would be realism if that could be achieved.
If units could be made more speciallised, then this could be made possible. If Triari were helpless if outflanked / or be very vulnerable to archery. If all units had a big weakness, then any balance army would always beat an army of one unit type, as they would be able to exploit that weakness. But this brings up other realism issues. *Sigh*