Re: better pickups for splitting?
In my opinion probably the best option for splitting is going to be the P-Rails were you can split to a good old P90, a rail single coil tone (imho it's kinda a cross between a tele and a strat), parallel humbucker (kinda like a PAF style), or series humbucker (relatively hot with a more contemporary voice).
Will it give you the same sound as a strat, a les paul with great PAF style humbuckers, or a P90 monster NO but I think it will give you a lot more flexibility than a traditional humbucker. Unfortunately I haven't found a pickup that turns a guitar into totally distinct strat, LP, etc tones. The P-Rails is the closest I've found but I still like having a guitar around with a nice vintage sounding set of humbuckers, I still like a traditional strat or tele, and so on.
My only other advice is that I've heard good things about the DiMarzio Bluesbucker being able to get good split coil tones but again I doubt that it's going to sound distinctly like a strat split and all that.
Different pieces of wood, different hardware (bridges, etc), different scales, different nut widths, and all that fun stuff really do affect the tone more than simply pickups.
A PRS McCarty, A Gibson Les Paul, and a Gibson SG are all solid body humbucker equipped axes but all three have different tones.
Likewise a Strat and a Tele are both single coiled axes but they have very distinct tones.
To really get distinct sounds you have to have different instruments. Hopefully I didn't rain on your parade or anything but if a perfect pickup existed like what we all want there probably wouldn't be so many pickup mfrs and models available out there likewise there wouldn't be hundreds of different guitars of various shapes, sizes, and materials.
