a)Yeh it would make no difference.
What about claimholder bandits? They have the colour like questbandits, and have their own ... lets say it troop trees. If someone revolts against england they will have a english troop tree.
There are no claimholders in 1200, you can just intrigue another guy to the crown ... i think. And if you play for example Czech, the Prémyslid dynasty there should be a claimholder of the Kings dynasty, its would just be the name anyway. And the claimholders dont appear regulary, maybe just one guy at all. If he fails theres another guy at another kingdom.
Maybe also something like; The claimholder is on the open field or tavern and acts like a customer.
b)
Yes please. If its a border fief, between two cultures the player can influence it a bit by the Villageelder.
And also for the noble troop tree; I want to enlist in a lords army as a noble. You just get the regular seargent troop-tree which is quite nice but you end as a man at arms.
Maybe if you just choose your nobility in the character creation.
If its possible it would be nice to have both