Am I the only one that though this was a suggestion for make up to be added to the game? (facepaint / war paint and such) :D
The problem is that not everybody who got riding skills is using a horse. They probably just play inf aswell.
So a possible Solution would be to ask every player in the beginning not only for " Choose Team", but also for "Choose Class".
Problem: Trolls.
Well, cant simply players be sorted if they have cavalry skill or not. which make them "cav"-sorted.
Ranged (crossbow/archery wpf) get "archer"-sorted (if not already "cav"-sorted)
If you have alot of archers and inf on your team, but no cav, it will appear for everyone that running in the open is not that possible for intance.But wait, how is that not obvious enough even without your suggestion being implemented?