A different UY will be a completely different membership. You will not be able to combine points from both memberships for a single nights stay without doing a transfer from one contract to the other.
I think that as long as the contract you are considering is big enough to cover whole nights for what you want, then it is doable.
We had it one time but we didn't own enough in either contract to book our entire summer trip at the 11 month mark without borrowing points from one of the other.
Good luck!
PS Since today is the deadline, if it were me, I would make sure that the contrat that you sign specifically indicates your right to back out if it does not make it to Disney in time to keep the trading benefits, if that is something you want with these add on points.