I wonder what happens after battle if a cavalry unit loses their mount. Will you have an unmounted knight joining with the infantry until you give them a new horse? hmm.
I don't think that for upgrading troops we'll need a particular type of horse or camel , for me it would be easier to do so with a simple horse.
The same I think should be, and as I presume is, in situation when troop loses their mount. Mount should be reinforced with the first in queue horse or camel that is present in inventory. Looking for special kind of mount after the battle when you are on enemy territory will effect that in no time your mounted Vlandian heavy cavalry squad ends up like a band of pikemen using lances as pikes.
Going back to Piconi's opinion, I hope that there are some minor or special troop trees because, as we could see on gameplays, the have to be cataphracts somewhere.