I don't know much about all this, but, couldn't the Alesis AI-3 be used as an interface with the FD-8 and solve the problem of being able to simultaneously record more than 2 tracks at a time? Using this optical interface, 4, 6 or 8 tracks could be simulataneously recorded. Does this make any sense to you "Pros" out there?
I know they promote this AI-3 as a good interface with an ADAT machine. But the FD-8 also has this Optical Interface, so why not eliminate the middleman?