Training for Units and the Ability to Command Them
Just a quick idea: we've had some posts cover the concept of a "Leadership Rating"/"Command Rating", as well as "Supply Ratings", etc. with the idea of abstracting the level of management required to support armies of various sizes. This is captured by the "Logistics" abiilty in GalCiv2, for example.
As a subtle, but useful, additio to this: I think units which are better trained should require less "leadership"/"command"/"logistics". Well-trained soldiers likely have good small-unit leaders, and thus require less supervision. Thus, all other things being equal, a better-trained army can be larger than a less-well trained one.
As always, thoughts and criticism are welcome.