I'll think you'll find the days of Xtensions embedding themselves, like Pasteboard XT, did are long gone.
Obvious test would be to load the Xtension, make a file, unload the Xtension and try to reopen the same file. You could do all this on the same machine, no need to send the files out. I reckon it'd be fine.
Only obvious potential problem is if the Xtension does something really clever - say a better drop shadow - which may be lost without said Xtension, the file will probably still open but the effect will be gone.
Greg
I think therefore I am, you're pink therefore you're spam