Droid X has 8 gb of internal memory. In theory you shouldn’t need an sdcard for storage. So use adb (i.e. adb shell):
umount /sdcard mount -o rw,remount / umount /sdcard ln -s cache /sdcard
It’s just creating a symbolic link. If you can’t do the ln command, get “root explorer” app, go to root, and click “remount as r/o” on top. The commands above should work.
However, it will only work until next reboot, Plus, camera will still not work despite /sdcard being an actual writable directory.