They need a completely new UT, nothing related to the Kipchaks.
Besides that if they want to implement a mercenary feature into the game it has to be gold based, having Kipchaks cost ONLY gold for allies, Instead of 60w 35g it’d be 95g, and Elite only.
But developers wouldn’t do that since there is a gold-phobia / obsession in the AOE community, everyone wants a gold efficient unit/design.