I doubt this will get done on Xorg any time soon, there is very little incentive for anyone to do it when it's already working much better on Wayland. The problem is in finding someone who will do it, it's not really a problem to figure out how it could be done because we already know that: just copy the Wayland API back into X. A good way to start would probably be to get scaling working in XWayland applications and then backport from there; amazingly, we're finally at the point where Xorg is playing catch up to Wayland in terms of features. I can't understate how huge that achievement is for the Linux display stack.