Those infantry guard of Jerusalem gave me an Idea, since you guys are already doing recruitable generals, could some factions recruit generals on foot? For the Ghorid, Ghaznavid, and Kwarehzm you could get Daylami chieftains with a retinue of the finest tribesmen; Constable/warden of the city for Outremer etc.
It would make defending walls a lot more fun, as well as just being a pretty distinctive feature to further set BC apart from the crowd.