As far as sending hexaphonic signals from the guitar to an outboard processor... Roland's already doing so with a number of their products. And they always seem so close to getting it right. What they did with serializing hex over 1/4" TRS is great... if only they'd managed to squeeze audio (mag pickups) over that same line... and if only they hadn't dumbed down the switching on the (still ugly) guitar wart. If they find just a little more bandwidth, miniaturize and/or dress up the pickup interface so it either disappears or adds value, and then introduce the next gen of GP10 or whatever... they're essentially already there. (Line 6 is probably quite aware of this, and looking skeptically at the potential profitability of a 3rd generation of Variax.)
I think all this technology could already be working much more elegantly. I mean, there's multichannel audio interfaces sending everything through a single USB connection with minimal latency already (not talking about the actual guitar processing here, just what's needed to route your signals to and inside, say, an 8 I/O interface). Hence, any standard USB cable would already do. With the advance of also supplying bus power.
Also, if you expanded that idea, for standalone operation, the interface and processing themselves could already sit in the guitar (as is the case with the Variaxes), so in case you wanted, you could as well use your guitar as an audio interface (the Mooer GTRS guitars are already doing it that way). Just add a laptop to expand your sounds. And maybe an additional audio breakout box should you not want to run mutliple cables from your guitar. Such a breakout box could also double serve as a controller input module, allowing you to connect all required switches and EXP pedals.
Latency shouldn't be an issue, either, given that you can, say, buy a lowly Motu M-series interface delivering 3.5ms of RTL.
Such an approach would combine all options and allow you to do incredible things.
I have once played through a setup that was splitting a HEX pickup into 6 discrete signals (there's been a handful of breakout boxes years ago already, no idea about what exists today), all then running into an RME interface, ready to be processed individually - and if you ever played through something like a poly distortion (maybe even enhanced with a dedicated filter per string), you instantly know that you possibly don't even need much "real" synthesis anymore as the options are staggering already.
Doing all this with what is a standard computer is a fantastic thing anyway as you could simply use each and every plugin there is for further processing.
In the end, there'd be plenty of ways to realize things, just that there seem to be very little incentives for companies to actually do it. And given the niche character of any of these units (regardless whether it's Variaxes, SY-300/1000 units, VG devices and what not, let alone MIDI guitar setups), I have some strong doubts we will ever see any truly serious attempts at this technology.
I mean, the last time I've seen anyone using any kind of Variax or GK equipped guitar is so far away I can't even remember it anymore.
There's not even many SYs in the wild - and those don't even require a modified guitar, so if all this stuff was popular among guitar players in general, we should see much more of these things on pedalboards.
I already said so quite often: Guitar players seem to be the most conservative bunch of folks when it comes to exploring new sound options. Heck, even bassists and drummers are more innovative.
