You can wire any 2 conductor pickups to be out of phase (after all, it was done with Peter Green's 1958 Gibson :roll: )
You can if you have 2 conductors (connected to the ends of the 2 coils)
plus a separate ground wire (connected to the metal baseplate), but isn't BKP's "2 conductor" wiring actually a single conductor plus a braided shield?
In that case you can't just reverse the connections and use the braided shield as the "hot" wire, because it's connected not only to the end of one coil but also to the metal pickup chassis.
I believe Peter Green's pickups ended up out of phase because the neck pickup was dismantled and either the magnet was reversed or the coils were rewound in the reverse direction. It wasn't anything to do with the way the pickups were connected to the pots.