If GNOME is overkill for a 260x140mm display, rather than rewriting all your apps, you just slap a different WM on top of it.
I've never bought that argument. It takes more than squeezing a non-trivial desktop app into a small rectangle and slapping a barebones WM on it to make a usable Handheld UI. Hell, a number of GNOME apps I've seen have problems on an 800x600 screen at any size.