Reviving an old thread...
I believe Elliott was an ISFP with developed tertiary Ni. He had his intellectual pursuits, read a lot, according to friends.
But he seemed more Se than Ne. He played basketball for fun, his music showed a particularly dexterous and kinesthetically-in-touch quality, whereas INFP musicians tend to create music more chaotically, as others have mentioned.
Jim Hendrix seems to have been an ISFP, and I see in them a similar Fi dreaminess, individualism, emotional depth, and an outcast/outlier quality as well. And they certainly show a similar Se connection with their instrument and the rhythm, melody, and harmony of music. They both are like machines in their virtuosity -- watching them perform live really conveys this best. Although, Elliott often, especially in his later years, would mess up his songs and sometimes give up on them or struggle through them, seemingly addled with mental health issues -- addiction and perhaps C-PTSD. So, you can see his virtuosity shine and you can also see the struggles he had in the way he sometimes performed on-stage.
All that said, I see Elliott as surely Fi-dom and almost as surely Se-aux. I believe his interest (according to friends) in complex reading subjects was perhaps due to his developed tertiary Ni.
Thanks for reading, and I'm curious what y'all think.