I think this new vow system could be actually very fun, if the bonuses for getting one would be worth it.
Pls give them campagin bonuses Bretonnia curently lacks: for Questing vow: add +5% replenishment rate.
Grail vow + 5% replenishment rate +2 recruitment rank to all units.
None of their blue skill tree has something that gives them bonuses to recruitment rank ( only bonuses have knights via chivarly system).
I think that given the fact that getting those vows are a lot of trouble, giving them really meaningful campaign buffs bret lacks also replenishment rate bonuses and recruitment rank bonus for all units (or even just for peasants, cos we all know that grail knight will always attract some rubble of filthy peasants) would be actually really beneficial.
Questig vow for Knight Lord is just laughable +5 AP dmg, it's not even 1% of AP dmg for a Lord.