Just some quick thoughts, perhaps not as complete as they could be. -- Len Ovens
Doing pretty good I'd say, Len, I have been periodically studying this for quite a while. And now that Firewire is going passé I have to do it again :-)
There is one hardware approach which I have not seen at all yet: this is combination of (say) eight simple stereo USB interfaces, into one box. Shouldn't it be fairly doable, to take eight satisfactory-quality USB interfaces, wire their timing chips together,
write a custom driver, and go? Or don't bother with the timing chips and the driver and use zita tools or multiple Jackd processes, and build this with a Raspberry Pi (or one of the more powerful act-alikes) as a jackd-over-tcp/ip audio appliance?
There is the fact, though, that USB2 and before, are monodirectional -- half duplex. They transmit data only one direction at a time. Yes, they flip back and forth very very fast, but no matter what, that's not good for us. But USB3, happily, now gives us
a full duplex capability. Perhaps this will mean that once small-studio-priced USB3 multitrack interfaces come out, they may be simpler, and therefore potentially less expensive?