breathe
Refugee
Ow would you do this?
Get 6 more strings.
most harmonizers can do it but they do sound a bit synthetic and leave some 'odd' overtones.
The jangle box could help get a jangly rick-ish tone. But not necessarily a 12-string.
http://www.youtube.com/watch?v=hjfmp3alppy&feature=related
fender makes a vg stratocaster. It is a 'modeling' guitar. It has a knob for 'tunings' and 'modeling, similar to a line 6 variax.
It mimics strats, teles, humbucker pickups (gibson), 12 string...
here's a demo:
http://www.youtube.com/watch?v=7ooaxufuo2g
link to a review of the vg:
Electronic Musician reviews the Fender VG Stratocaster | Electronic instrument models different electric and acoustic guitars
the tribute edge in joshua tree has (or at least had) one. While it isn't a main stratocaster for most shows, i know of him using it when travelling to farther shows (long distance/flyin involved) - where toting multiple guitars isn't practical.
My gripe with the POG and 12 string is that the B and e strings aren't an octave apart on a 12-string guitar, but the POG makes them so.