This is something you could do 10 years ago already on amigaos (with older versions of course) with geekgadgets.
There are a few X11 servers available for amigaos, geekgadgets one, amiwin (shareware) and xami.

Basically someone just needs compile native X11 sdk libraries so that upper layers such as gtk can be compiled and at last high-level applications like abiword.

Now, do we really want to run sluggish alien linux applications on a separate screen, with very little integration?