Blazer,
Yes, they sound pretty darn good when Jack is manipulating one. You must admit, though, that the singularly muddy tone is what they are all about. Jack is playing in a trio, where there is room in the mix for a bass that goes thud.
I have to admit that I'm probably going to pickup one of the Chinese Hofner basses and string it with flats, to get just about that same tone (McCartney, anyone?). Speaking (typing) of which, I believe I'd like to get a lefty, and learn to play it lefty. I think it might be an interesting exercise that would do interesting things to the way I approach the instrument. Good idea? Bad idea? WWJED? (What Would John E. Do?)
Back to the subject at hand, JE seems to have been heavily involved with many builders of basses, and while having lots of input with them they surely would have given him ideas in kind. He's regarded as the brain behind the adjustable nut, but I suspect that if not for the Alembic elves it would not have appeared when, how and as it did. Also, I believe that the sounds he got from his Alembics (and the extreme playability) gave the rest of the music world a benchmark to shoot for (still unmatched in my opinion). Of course, all the explorer/exploiter/buzzard basses seem to fit HIM rather than him adjusting to THEM. I wish he were still alive.
John