I haven't seen any mercenary elephants yet, but I buy up the Turkopole horse archers every chance I get. Also, I still only have one general in the middle east, so I haven't really sent him out venturing much, ha.
Does anyone have a good strategy for controlling those elephants when you're being sieged? I'm thinking about the only good option is cannon towers, seeing as how archers don't do anything to them at all, spearmen get thrashed, and your own artillery is mostly useless inside a settlement. Too bad the AI seems to always destroy all of your towers with their own artillery before assaulting. :(
I suppose mortars may work to some extent...
Actually once I had a citadel's defense set up perfectly, with units positioned throughout the different rings, and artillery positioned that it could actually fire upon units coming inside the walls, -and it seemed to be working pretty well, but then the game would CTD every time the elephants got inside the first walls... And that was AFTER the patch, ha.