I still think libhybris is a game changer for supporting other devices. I'm seriously thinking about a pi2 with touchscreen at the moment for testing my *little* side project, but if I can get it to a reasonable point I will be looking more at libhybris for other devices. if a decent, open intel x3/x5 based tablet with intel supported gpu driver comes along...

A tiling WM could work quite well if allowed to do full and horiz/vert split. Just needs a little UI polish compared to some existing ones.

As some of you know I've been experimenting with hildon/gtk3. At the moment it is still running on a matchbox2 based hildon-desktop. One idea I had as a possible future direction is to take inspiration from Harmattan and Budgie and use mutter.

I have a very small test app that literaaly just gets mutter running but has no ui elements (taskbar, switcher etc) using Budgie as a reference. Obviously there are a few gnome dependencies, as there are with Fremantle, but mutter could make a good start for you.

Alternatively, my other option should GTK3 prove too much of a hassle was to dump everything gtk and follow the Maemo>Meego path and use qt+qml. Down this route I was thinking what about expanding the qmantle2 demo (if you can find the source code, might have to contact rburchell directly). It uses lipstick iirc so you get a qt5 wayland based ui. I did have the source code but have misplaced it or deleted it by accident. You could mix in either stock qtcomponents or create a custom set based on marxians hildon versions.

anyway, thought I'd share some of my ideas wih you. also just reminded me i still haven't pushed mb2/gtk3 to github. one day i'll remember..