Polygamous divorce doesn't necessarily mean that everyone goes their separate ways. Rather, it could be that one person leaves (and generalize it from there). One or more people want out, and so execute some exit clause in the contract. What, if anything, they take away is settled at that time. Just like a partner leaving a three or four partner company.

It's not a majority vote under monogamy, by the way, so why would it be under polygamy.