On a two humbucker guitar, you can't really get the quack, but you can get a different kind of quack that is good enough for most people who want an "all-in-one" guitar (if I'm honest, they don't tend to be that demanding - the guys who want it RIGHT will bring a second guitar, or a third, or a tenth!) by using one coil from each pickup. Normally, when using two tapped humbuckers, I use the screw coil from one and the slug coil from the other so they stay hum canceling, but if you are doing an out of phase thing you need to use either both slug or both screw coils. I have a Super Switch wiring diagram somewhere that gives you:
1) Full neck humbucker
2) tapped neck and bridge, in phase, in series (I think - might be parallel)
3) Neck and Bridge full out, in parallel (Just like a Les Paul - one of the things I don't like about PRS's switching is you don't have this sound, which is one of my favorites!)
4) Tapped neck and bridge, out of phase (both slug coils), in series (again, I think, it could be parallel, but I don't think so)
5) Full bridge humbucker
I've used that switching a lot for guys after an "all-in-one" guitar, and they seem happy, but it has a (to me) big problem - the out of phase position is a BIG volume drop, and there is no way around it. Most of the guys I have done this for don't seem to mind, as they only usually use that position for rhythm work, so they can switch to one of the louder positions for solos and it works fine for them. I know at least one guy gigging 5 nights a week with this setup, so it seems to work well for him! Personally, I'd rather carry two or three guitars. But then, I make my own guitars, so there is a different cost thing going on, and I don't mind just carrying them around in gig bags because I'm not that bothered if they get dinged up. I can fix it.
Gabriel