I've heard you can wire two single coil pickups in series so that they sound like a humbucker, Now am I crazy to think that the same could be done with two hot rails? For that matter, with two humbuckers?
You can wire up just about anything series/parallel/split/out of phase... whatever.
Check out the Jimmy Page wiring scheme or use some Triple Shot mounting rings for more versatility.
That is similar to what a humbucker is in the first place...to coils next to each other wired in series. It increases output and makes the tone less bright. You can wire a rot rails, or two humbuckers, or any two pickups you want in series, but if you wire two already dark pickups in series you're going to end up with a very muddy sound.
Oh, and lotsa folks equip their Tele with a 4 way switch for exactly the option you mentioned. Meatier sound with more output than the standard parallel 2 pickup middle position.