Hi i'm thinking about this problem all the time. personally i don't like upgrades since it's absolutely not realistic and SID's team made it just to make their way easier about making units obsolete ( lol, joke ). any way, while i'm keep working on updates for my mod i've decided to ask public - would u like to have "upgrade" function for most of the units in ur civ4 game ( or my mod ) or u r ok that AI builds old military by having the new ones only because units are not obsolute since it's not upgradeable and to keep ur game ( my mod ) with not upgradeable units to play!? p.s. playing by Canada in my mod i have more modern army that my neighbor on south even if yankees have twice more modern technologies ! all this only cause AI builds cheaper stuff instead of strong one ( have no idea why ). p.s.s if someone can help me to make units "obsoleteable" that will solve the problem ... but no one has yet!