Thank you for your comments. Just to clarify: the another alternate 12-string tuning I'm referring to involves a standard tuning plus an alternate tuning of the additional strings provided by the "parallel pitch" function. Or, to accomplish this another way, alt tune the "main" strings and standard tune the "parallel" strings. Either way, I think this is only 6 pitch shifts (unless the code to create parallel pitches is so lightweight that it can only double the existing pitch, in which case I guess you're correct in calling this "12 separate pitch shifts"). Either way, I hope there's adequate DSP power to do it someday. It's a nice effect.
I mistakenly read between the lines when researching the JTV Variax guitar and assumed that its ability to simultaneously use alternate tunings and emulate a 12-string guitar would allow me to use intervals other than octaves for the latter. The Workbench graphics for Tuning and Parallel Pitch look so similar that I figured you can enter a "Parallel Pitch" value other than 0 or +12. Not so. Here's a tuning I'd like to use: E2/E1 A2/A1 D3/A2 G3/D4 B3/F#4 E4/B4 Since my ancient Roland VG8 could do this using its Polyphonic Pitch Shifting feature, I'm astounded this limitation exists. Any idea if Line6 will add more granular control over Parallel Pitch tuning in a firmware upgrade? I realize I can mix in the mag pickups and achieve the same tuning without involving the "Parallel Pitch" feature but that's a compromise.