I believe that for single player, a different option was possible. Civ and Total War proved it. In both games, you could build an infinitely large army...as long as you had the ressources to build and maintain them. If you built everything you wanted, over long term, your army crumbled since replenishing lost divisions was impossible due to lack of money. Huge army without planning meant train wreck of an economy which in turn meant train wreckt of a military too.
In multiplayer, could a similar concept be applied? I don't know, I fear that we're stuck with the old system for quite a while until some genius finds the ultimate "invisible" pop cap.