Make sure you have enough funding/money to patent it. Try find all pitfalls and caveats. At least patent 20 variants of it, so no one can come up with the same idea. By and large I've actually asked Paul Vo this question on his website by now. He was the one inventing the Moog guitar that had infinite polyphonic sustain on all strings, as well as the other way around, LESS SUSTAIN, which made it turn into some banjo thing. He actually has an own company now, doing this stylus sustainer that looks like a felt marker tip pen. Among other things. He did reply to my mail, but it seemed that he got too many other things in mind at the moment, and didn't think it would go down a bomb. I e it seems like those interested are more into some kind of NEW SOUNDS with NEW gear. "Mimicking" old gear or the idiosyncrasies of shorter decay on strings, seemed not to be of his interest. I think he's not playing bass at all, at least not the upright. All this, in spite of him actually knowing how to pull it off technically.
FWIW, I think a gadget like this has to be incorporated inside the pickups, freeing your hands. Paul Vo has gadgets that must be held or additionally attached to any guitar/bass body.
Now only if the method of capturing the "wood reverb" so to speak like they do on those Fishman Aura boxes would be fixed too, then I am all game. Fishman CEO is a bassist too, and would long for something like that to happen. As it is now, they say it's almost insurmountable to produce the same things on the lower frequencies. I e these two things should need to go together:
a) "Wood box" resonance like the Fishman Aura with "toneprints". Only, not from guitar, but from huge acoustic basses (of high quality).
b) Reverse sustainer, like the Paul Vo one on Moog guitar. Not endless sustain, but shortening it instead, especially as you go up the neck.
These two are - together - of paramount importance. Not either or. The first one MAY be fixed with additional pedal later on, and don't need to be a fixture gadget added inside the pickup cavity. Added option is, of course, endless sustain, if you care to play like that. There's actually one on YouTube who plays nice "hornlike" lines on a fretless bass and TWO E-bows taped together. So endless sustain may have its merits. But it's more of a fringe benefit than anything else.
