I’m in (almost EXACTLY the same boat as you) so yeah, this absolutely works. What you just described is almost word for word what I did/am currently doing.
I first confirmed I could do fast motions in excess of 190 bpm (check!)
I applied that to a tremolo motion on 1 string, pausing to change strings to get a better feel for how it’d feel on all parts of the guitar, but again, staying relaxed and maintaining tempo (check!)
To be clear, the string changes were tremolo - stop - pick a different string - start tremolo again - repeat
After a couple days I’ve been able to pretty much lock in a tremolo motion that I can repeat as necessary for minutes++ at a time well in excess of 160bpm (check!)
I’ve analyzed the type of motion I’m making for my current tremolo (it appears Downstroke Escaping) so I came up with a (dumb but simple) ‘riff’ that always changes strings after a downstroke and is a 3 finger per string exercise that just repeats the fingering patterns twice on every string after playing 5,7,9 one time on the low E.
Anyway, it turns out I can blaze through it picking, but my fretting is HILARIOUSLY slow because, like @michael_s said, my fretting hand has NEVER had to do anything like this before. It’s honestly comical. But if nothing else, it’s proving to me where the issue is now.