There are some real advantages to lower tunings, as most "open" tunings are. My favourite guitar for non-standard tunings is a 27" scale baritone. It likes the lower register alot, accepts a capo well if necessary, and gives me some alternatives key-wise that I can't get with other guitars. Open G, Em, and DADGAD, dropped down 3 or frets are nice, and once in a while I reguage for CFCFCF.

I also agree that 12 strings can sound great open tuned. Maybe I need another.

Peace, Mooh.