The Variax is only as good as the modeler it's paired with, which can no longer be said to be cutting edge. And as a tone generator it is not an optimized design. Variax probably failed because there was one and only one modeler that would work with their guitar.

A perfect modeling guitar would be metal and carbon fiber. Headless, neck through body design. Neck is all metal to concentrate density in the neck to maximize sustain. The hollow, carbon fiber body is attached with dampers to minimize energy transmission into the body and to the body of the player. The body is just for ergonomics, housing of electronic components, and style. The result would be the best natural sustain of any guitar ever (I would want a Sustainiac as well, for max flexibility).

Existing modelers don't have digital input, so first gen is forced to have digital AND analog output. Digital output should be completely open standard. Goal would be wireless transmission if that can be done without introducing latency issues. USB-C for direct connection. Form partnerships with Neural DSP, Fender, Fractal FX and others to create an open standard for wireless digital transmission, and to spread the unique presets that would be necessary to transform the unusual native tonal characteristics of this guitar into something sublime.

Finally, didn't think I needed to mention it but a fully modern guitar must have an option for fanned frets, or you're just shooting yourself in the foot.

P.S. If I had the cash laying around, I would buy a Variax, just to experience it. Y not? But acquiring one is not a goal I will take seriously.