Been following your progress, great work lupohirp and arjen!
We are having the same space issues on the VM670. Inside build/common there are make files for small languages and locations. The current macros don't override from device or vendor mk files right now, so you have to edit the build tree directly till the macros are fixed.
My current builds are just shy of 70mb, with only a few languages/locales, all videos and most audio files removed (left a dozen ringtones and notifications), all live wallpapers removed, and the bootanimations removed, as well as a modified Trebuchet with all xhdpi images removed.