Got a bit further with some help from mbuesch (menuconfig doesn't produce a working Xorg for some reason).

Is it inappropriate to get excited by seeing this?

It's not quite ready for end-users, but wireless works so I can ssh in and do stuff (the X keymap is worse than the console, not even ctrl works).

But first things first: charging. Stskeeps, can you point me to whatever magic you used to get the initfs bme working in Mer? I can only get as far as starting it (chrooted, obviously) and watching it segfault here :-(