extended range - per string outputs?

Look at why people use more than one amp, or why it's common to split the bass DI in metal. Granted it's not the same thing, but it's still a similar idea; you're processing different frequency ranges individually.

 

Per string output would be weird, but you could biamp your signal. It was a pretty common technique to run a really gainy mesa alongside a less distorted plexi. Getting articulation while still having girth.

 

Could be the future of pickups. More technology in the pickup itself. recording would give you each string output. 8 different signals. I'm not sure how you'd record that because a normal cable probably can't do that I imagine. We have technology like Ax Fx III which sounds incredibly close to real amps. So maybe it's time for pickups? I know there is like one pickup that does this. But I mean more advanced and better sounds. Something allows you to get something like 8 different outputs for the strings or whatever. If not 8 we can start with 4 outputs (two string outputs).

Though we are just speculating. I don't think anyone here (in this post) works on pickups or the technology behind it. Pickups haven't really changed since the 50s, maybe it's time.

 

In the sixties they experimented with magnetic pickups per string ... maybe it is time to bring that back ^^
compensated pickups + fanned frets could solve many problems for 8 string players imo
https://reverb.com/item/1622535-vintage-very-rare-japanese-guitar-with-6-pickups-stereo-output

 

Look up hexaphonic ("hex") pickups. This has existed for standard-range guitars for a long time. The Kramer Ripley guitar might be relevant as well - mixing of strings was done onboard the guitar with final output being "only" stereo. EVH used it.