This is a follow up on my nobel thread and its something of a suggestion.
IMO, it would be cool if a realm's army (landed regents) was divided into "household" troops and vassal contingents. Each ruler in the middle ages had a core contingent (like the housecarls, or the obsequia in Carolingian times) which served as his bodyguards and his principla unit(s) in a campaign. This was usually the elite of a regent's army, then followed the troops drafted or maintained from the king's private domains or demesne, and then vassal contingents summoned for a specific campaign.
What I'm proposing is adding a small entry to army units indicating their primary allegiance. Not to break game mechanics, units would still be maintained from the regent's treasury but there could be an additional trait regarding their origin.
For example
Aruvor Roesone, Baron of Roesone, Count of Caercas, Danaroene and Bheline has the following army units (all made up for the purposes of this example)
2 armsmen - household troops (elite bodyguards, professional troops)
2 infantry - royal troops (freemen, peasants and burgers from royal provinces serving in the army)
2 archers - royal troops (also freemen, peasants and burgers)
2 knights - royal troops (minor noblemen drafted from royal provinces, rotating in service so that some are at home, some in service - all done in the background without any bookkeeping)
1 cavalry (nobles from Duerlin, belonging to house Coriel)
1 infantry (freemen from Edlin - house Denoered)
1 archers (freemen from Abbatour - house Barden)
1 mounted infantry (nobles from Fairfield - Noelon)
1 archers (burgers from Ghoried - Siele Ghoried)
*burgers not as in hamburges but as city dwellers
It would take some thinking to decide on the exact distribution, perhaps the number of law holdings held by the regent compared to the number held by vassals or something.
Of course, each "named" vassal in the P&H would also have their own units based in their income. This "allegiance trait" would serve as a reference in case of feuds, disputes etc. So if there was a revolt of the burgers of Abbatuor, "their" unit might temporarily desert, or if a major feud erupted in Duerlin or in one of the royal provinces, a cavalry unit or a knight unit might become embroidled in it.