This time xwayland wouldn't have a specific compositor interface and would be a real wayland client, so it's simpler for the compositor.
I remember everytime a change to the shell interface code in weston was merged, xwayland for weston got new bugs (fullscreen broken, bad stacking, etc).
So this change will simplificate life.
devilhorns: since weston was only meant to be an example compositor, could this be called the first proper, full featured compositor? If so, what are the major differences making it so?
I still don't think KDE is at the point where they've finished deciding all that, but that was certainly their original plan. We'll see if they stick to it after they start implementing everything. The whole idea of a "system compositor" has kind of gone away, but they've replaced it with something largely equivalent.
linked blog post (from the second comment I quoted on the wiki), that's exactly what he (Martin) does.
From what I understood, they planned to implement the system compositor in the session manager (kdm, gdm, lightdm, etc.), which would make sense to me. Weston would be more of a stop-gap solution, to be used (for debugging/testing) until the DMs are "ready".