Ok, I do apologise if this sounds a bit daft, as I've barely played much with Empire (and use a Lietpold list anyway), but I was just looking at your recommended tactics section for Karl Franz and was wondering - is he really the same tactically as a regular General?
He's got a reasonable save (2+ on Barded horse, 3+ on Monsters, and 4+ mounted, and a 4+ ward), and a very nasty weapon, on top of some decent stats, so there's not a lot of combat characters willing to go near that. And though he's expensive, on horseback he's feasible with a bare-bones level 4 in some average sized games.
Plus, he can bring a Dragon to the table, which is a whole other ballgame in some aspects. Though if you're approaching that from the cost perspective I do see your point in not giving that too much thought...
I'm not saying he's good or bad or anything, but I do think he might provide a few alternative approaches to the Empire.