Compare MM and P pickups

Personally I have never played a bass with an MM pickup so there is little I can say. The MM is a true humbucker so it will likely have more output and more inductance than a P which is really a split coil pickup with the two coils in separate housings. If you put a MM pickup in the P sweet spot you could cover four of the poles, two on each half, with pieces of steel to neuter them and probably have a fair imitation of the P sound or the reverse P sound depending on which four poles you covered. But I think Bart makes a "quad coil" pickup where each half of an MM style humbucker is wound with split coils so that you could mix and match the coils in use to do a better P or reverse P impersonation. The Bart design makes a lot of sense, that is what I would go with to simulate a P pickup since it is easier to flip switches than to futz around with bits of metal to cover pole pieces.