That looks pretty similar to what I ended up with! In the end, I had Weston running a rootful fullscreen Xwayland as the only Wayland window, and then X clients

That looks pretty similar to what I ended up with! In the end, I had Weston running a rootful fullscreen Xwayland as the only Wayland window, and then X clients within that. There were still some complications, since I also wanted to make use of some GStreamer overlays that could totally sidestep window management, and the result wasn't perfect but it worked fine. Still, I can't help but be somewhat unhappy about how the forced use of Wayland resulted in a fair amount of work, the end result of which was running X clients anyway and trying to pretend Wayland isn't there.