It is possible to install X11 on an SD or CF card for the 5x00, and there\'s special versions with debian available based on the OZ kernel, and it\'s all been done. I have personaly installed X11 on the original TKC and on OZ, but to be quite plain, it sucked.
There simply aren\'t enough pixels. You can\'t zoom in enough to make it good.
Even this current cacko X11 rom, which kicks butt by comparison, has some major drawbacks and room for improvement. A number of critical and every day functions (like right clicking) are far from intuitive from what i hear, but it\'s a giant leap in the right direction, and I would imagine that most if not all of those issues will be resolved in the next release or two.
The other problem is the native apps you mentioned. Most native X11 apps will run fine in VGA resolution like on the 760, but to have most of them rom on a QVGA screan requires a partial rewrite of the program before cross compiling. ANd of course, reguardless of which device you have, X11 is a complete and total waste of time without a large memory card.