I think the whole army issue between a bug and a feature has to do with the level of war play in the game. The scope is strategical but the wargame is tactical or more than often to small units. It think it needs to follow this scope or else it would not be a civ installation. When the AI win unfairly, when it cheats, I remember that it is playing a low-unit tactical game and certainly not the same game as we are!
I won't enter in my grognard theories or even if I am truly such, still after all this time, I'm getting pretty sure that no upsizing or downsizing can reasonably occur in a computer game between strategical and tactical gameplay.
But it is tempting! Oh, so it does! A very marketable trend, AFAIK without any irony.