Gotcha. For Les, it hadn't occurred to me that it'd be a problem if you weren't in the heat of the moment, but I guess I do see that if you were having pincer problems it'd be a pain. For Alan, I guess I'm stuck in a coverband mentality. I gave the Zappa tune a listen (I'd never heard of it before actually). My first reaction was that it sounded like a strat throughout...but your greater point I think is that if the guitar offers the potential, and if your creative muse tells you that you should be splitting the coils in and out, then why not have a knob that lets you do it exactly when you want to.
All very enlightening to me. I was at practice this evening with the band and decided that I was going to find a song or two where adjusting the split mid-song would be good. Worked out fine, but the songs I picked wanted splits except for the solo, which seemed like it might accommodate humbucking mode. Entering into the solo, where the timing was shorter, just required hitting the knob with my palm, which was easy. Going back to split coil, there was more slop in the required timing, so I didn't notice it being difficult, but I could see where it might be.