This does seem to be an unfilled niche in the audio world, and probably why so many tweakers exist to modify existing carousel players. I'd probably start with one of the Sony carousel players(the 555 maybe?) that does SACD multichannel and have someone like Stan Warren or Dan Wright modify it for a few hundred bucks into a killer transport that would probably compete very favorably against the high-dollar units mentioned above. Best of luck.
Tim
Tim