Hi!
I think when joinging a faction as a vassal, start a quest where the player has to prove some loyalty and skills by helping the ruler in some way. For example, attack a hideout close to his domain, bring X soldiers of type y to his garrison i Z or something else that requires a bit of work by the player. This can be one quest ore several chained quests, but at the end, player is rewarded with a castle, the one with lowest prosperity that the king owns. Or if he controls non, the poorest in the realm that is controlled by a lord with at least 2 holdings. Only, it must be of the faction culture.
This solves 2 issues with vassal gameplay I have found:
1. You currently likely never see a fief of faction's culture(unless you play Empire)
2. You can step right into the lordly life and not do all the workshop/smithing/trading/tournament stuff first if you want.
I think when joinging a faction as a vassal, start a quest where the player has to prove some loyalty and skills by helping the ruler in some way. For example, attack a hideout close to his domain, bring X soldiers of type y to his garrison i Z or something else that requires a bit of work by the player. This can be one quest ore several chained quests, but at the end, player is rewarded with a castle, the one with lowest prosperity that the king owns. Or if he controls non, the poorest in the realm that is controlled by a lord with at least 2 holdings. Only, it must be of the faction culture.
This solves 2 issues with vassal gameplay I have found:
1. You currently likely never see a fief of faction's culture(unless you play Empire)
2. You can step right into the lordly life and not do all the workshop/smithing/trading/tournament stuff first if you want.