Let me try a different tack.
Is there a way we can give the player a visual cue that he needs to upgrade his light cav that's as effective as the difference that currently exists between obsolete and current units in the build-queue or the unit itself?
Better still, is there a way to make the upgrade automatic, like instead of having two units, have one unit that receives the noted 20% attack bonus with Nationalism? Or is the travel requirement to and from a barracked city a desired side-effect?
P.S. I'm surprised at the resistance to the reuse of existing artwork for a new unit in the mod - it's not like we'd be using snapshots of horseriding barbie, but existing, included C3C assets. I think I just don't understand certain aspects of Stock Civ3 Flavor. I surrender, though. I just don't understand the argument.