Why not solve the problem with marriage

Prior to leaving Mereen she mentions that she is leaving Daareo so he does not stand in her way of a possible marriage in Westeros. Now, we know that she nor Jon is aware of their relation, but they seem to trust each other and like each other.They need to be helping each against their two major enemy's. Why not unite the north with South by way of marriage. They could be co-monarchs or allow the regions to keep their sovereignty but each monarch would be a consort to their spouses region.