I realize that most guitarists are not interested in carbon fiber instruments, but it might be worth considering for instruments like this. For instance, check out this
Emerald 12-string baritone/bass, tuned E to E (an octave lower than standard with all octave courses). This
video gives an idea of what this is capable of. I would think the 30.5" scale would be perfect for a typical baritone tuning.
Just something to think about.