If the 11/7 month booking windows for the whole resort hold for both existing and new associations, then this would be technically doable in a much easier way: instead of extending, trade in old points for new points with GW.
If the booking windows were the same, this would be the only case where it was necessary to do so, so it wouldn't cause a slippery slope.
The biggest issues would be:
1. cost assuming extensions would be at a significant discount for current owners. If a current contract could be extended for $50/point, and new points are $175/point, then
DVC would have to give a trade in value of $125/point to make this so. It probably wouldn't be such a large number of transactions for this to bother DVC, but there certainly wouldn't be any profit on the table to make it a likely outcome.
2. MFs. Even IF both associations share booking windows, and that's a big if, they almost certainly cannot legally share the same MFs. The new resort will likely have larger fees (cabins). So, agreeing to swap into new points for a GW will mean the owner is not only agreeing to a 10% point premium, but also agreeing to higher MFs. I don't think many owners would want that, that would make for far fewer willing swaps, and that again makes it less likely that DVC would bend over backwards to cater such a small owner base.