From the beginning I did push back against the common assumption they couldn't do what they did with Riviera (before we saw the details) because they would do it with a new agreement. What you are proposing is modifying our current agreements, something that
DVC hasn't attempted to do to the detriment of the owners. The only major one, I know of, was the change made to the agreements to allow for the change of UY which I find to be in the betterment of every owner and DVC alike.
I do trust they won't likely give resale and direct owners different home resort priority periods to all existing resorts because of the changes required and Florida wouldn't take too kindly to it. I also find it highly unlikely that Florida would ever approve a new resort with this rule, but I won't say never since Disney has a lot of pull. Is this something that current timeshares do? I haven't heard of any like that; the current resale restrictions I've heard similar to other timeshares, but never modifying the home resort priority period.