I reckon the way to represent the differences between the various knightly orders is with magic banners. We already have a banner for the White wolves, albeit one that needs its rules adjusted. Other examples might be
Banner of Myrmidia: For blazing sun, this banner allows the unit to redeploy, in recognition of blazing sun's tactical prowess
Reiksguard banner: Extends the leadership of the knights to units within 6"
Morr: Immune to fear and terror, or immune to fear for all units within 6"