What about relative pointer and confinement? I believe that is
important to have it working.
It is actually already there, with support in mutter/gnome-shell and SDL2 so if you run a
native Wayland game, it would work already.
What's missing is Xwayland support, but there are patches from Jonas already available
upstream, of which those which implies an ABI change are already merged in xserver-1.19,
so that it can be added later without causing an ABI break.