I can imagine how it would seem comical to a guitarist, knowing how closed-minded many of them are. Well, I guess that applies to bassists as well. And audiences.
The only thing I would have against a 12-string is that I would have difficulties playing the lower notes. I have always been an advocate for extended ranges but 9 strings is about as far as I could go without having to reduce the string spacing. I rarely feel the need to play on my F# string so a high Eb would be fine with me. I would be quite happy with a 9-string tuned B to Eb.
For two handed tapping purposes, I'd prefer a Warr Phalanx if I wanted to get extended ranges. That way, the bass notes would still be easier to play and the higher notes would also be accessible without worrying about hand crossing.
- Dave