Anyone ever seen a Baritone 12 string? Is it even possible, or would that be too much tension for a neck? If it is possible, what about a twelve string bass? Imagine how thunderous one of those would sound.
If they can do this then I bet they can do anything.
http://alembicguitars.net/info/fc_trip.html (http://alembicguitars.net/info/fc_trip.html)
Hmm, after seeing that I am beginning to wonder about a sixteen string . . . eh, maybe not.
Although I can't recall ever seeing a Alembic baritone 12, I know Billy Sheehan used a Yamaha as well as a Renaissance baritone 12 on his (first) solo album Compression.
Renaissance and Veillette both make baritone 12 string electic-acoustic models. I think Veillette also makes a purely electric version too.