I don't think this is anymore a valid concern. From the Wayland FAQ:
"How can I replace Wayland's Window Manager?
The Wayland architecture integrates the display server, window manager and compositor into one process. You can think of Wayland as a toolkit for creating clients and compositors. It is not a specific single compositor or window manager. If you want a different window manager, you can write a new one. A 'libweston' effort is underway in order to allow new environments to reuse Weston's codebase and mechanics, whilst providing their own look and feel."
There's a handful of Wayland compositor frameworks - including one built by the KDE project - and Weston provides an interface by which custom UIs can be created. I don't think there's going to be much of an issue, aside from potential problems with the spec itself.
"How can I replace Wayland's Window Manager?
The Wayland architecture integrates the display server, window manager and compositor into one process. You can think of Wayland as a toolkit for creating clients and compositors. It is not a specific single compositor or window manager. If you want a different window manager, you can write a new one. A 'libweston' effort is underway in order to allow new environments to reuse Weston's codebase and mechanics, whilst providing their own look and feel."
And here's a list of "alternative" WMs already in progress for Wayland/Weston: https://wiki.archlinux.org/index.php/Wayland#Window_managers...