Hmm, reset on any ennoblement of the village, or only someone else's ennoblement?
Simple example gameplay consequence for resetting on any ennoblement:
You summon militia to cut a noble train as a last ditch attempt at keeping the village, but yet another noble train is inbound. You noble your own village and up pop another batch of militia ready to defend.
Is this a realistic/undesirable danger, or am I looking too deeply into this?
Keep in mind that worlds will probably have varying militia settings - some may keep militia available up to 5 -10 villages, and allow for summoning more than a maximum of 300. A one-size-fits all solution is preferable.