remember how we resolved the lack of space issue when we hacked full blown ubuntu onto the Atrix? The external sdcard was partitioned into:
a 1st partition that was an msdos fat32 partition that served as the storage space available for use as the ext-sdcard
and...
the 2nd partition, was a hidden linux partition (so, for example, a 32gb card with an 8gb linux partition would report itself to the phone as an 24gb sdcard containing a fat32 filesystem) this hidden partition contained an iso file that held our full-blown ubuntu install - early in the phones boot process that iso was mounted via a loop device over the root directory of the very minimal system image.. thus we got past the space limitations imposed by the phones internal storage space limitations
and, changes made to the full blown system did not affect the minimal image - so, on the frequent occurrence of borking the full install, we just rebooted without mounting the iso and used the intact minimal installation much like a factory recovery partition.
A nice script was developed that automated building the full install from the minimal by downloading the packages, modifying the config files and rolling it all up into an iso..
perhaps this situation could benefit from what we learned from the Atrix Webtop