The difference, at least to me, when we say "guitar modeling" is that after all the electronic magic, the signal coming off your regular guitar 1/4" cable is transposed and transmogrified into whatever guitar you're pretending to play. I.e., Variax. So you'd have something like GK to this guitar modeling box, with a line out into your favorite Fractal Axe-Fx device.
Now that I think about it, I'm guessing that sort of box might require a new GK pickup, because maybe the GK-5 is ?only guitar-to-midi. Unless it's also carrying the raw analog signals the way the 13-pin stuff seems to have worked.... That sounds like an awesome thing for someone to delve into; just how many of those 32 channels is the GK-5 using?!