Suggestion ability to change flags in vassals

we are effectively building a nation and across history when a place is conquered they always have the flag of the conqueror flying above them after the battle i would love to be able to do this in the mod however after conquering a settlement and making it a vassal we cant change the flag it says all resources are being used by an outpost its just an immersion thing but i think that it would be really cool to be able to change the flag over vassals

I second this. No reason not to be able to change the flags.