I don't know if anyone makes this, and I'm curious as to whether it has any mass appeal:
I'd love a guitar designed to be tuned a wholestep below standard tuning (6th string D, etc).
The size, scale, etc would be about half way between a standard guitar and a baritone.
I know you can tune a "regular" guitar down, but this way, "drop D" would give you a low C. And you could tune this down a halfstep (or more) and get into the range of a baritone guitar.
I think of this as a "Bb" guitar, as it would sound down a wholestep from "concert" pitch, like Bb wind instruments. (You'd be able to play along w/ a trumpet or tenor sax player, and read right off their charts.)
Signature model? Mine would be a jumbo (maybe Gibson or Guild); maple top, mahagony (arched) back & sides, rosewood fingerboard.
Keep dreamin'!
~CC