Well I believe it simple enough to do (as you said) and mentally apply a x10 or x100 base for each troop and leave out the commanders.

Even at 100 per figure, it would take 200 units for 20,000 by that estimation. 200 units is quite a large army And 200 units on the battlefield is quite busy.

As some have stated before, I don't find imagining these types of mental applications very hard as compared to a game like AoW:SM, WC3 or any other RTS, or TBS game that is currently floating around. Especially with how the units look and are equipped I lean towards more epic, than less.