[bill4807]

That's precisely what I wanted to try and do, but the optic cable from the beta I/O link would have to plug into a spare optic port on my main servo/PSU drive which only has one optic port (being used by the 3 axes)

Would be nice if I could swap out the logic board for one that has it, but I'm sure there's no way that would work either.

An i/o link drive does not use FSSB/fiber optic.
It communicates using I/O link. So it would be hooked to your fanuc I/O string.
Of course custom logic would need to be written.
The easier way would be to use a tsudacoma package, and control it through m-codes for indexing or RS232 for table execution.