I love my Scheff as is, with the stock lipstick pickups. But, I also like tinkering, and the idea of a 3 pickup bass! If I had your Scheff, I would without a doubt favor the neck J and P pickups. I might add in the bridge J like adding spices to my favorite dish. My other setting would be both J pickups 100% on and add in some P to taste and/or as needed.
That said, I have been pondering and planning a J/P bass project for weeks now. I have a minty (I bought/ordered the bass new) MIJ 70s F**der body that I stole the neck from, and built a J bass around. I don't get along well with the jazz, and don't have much desire to mess with it much. So, I'm thinking of mod'ing the P body by moving the Split P pickup closer to the bridge, and reversing it's orientation. And then I would place a J pickup close to the neck, like the Scheff. And then, I would have to cut a new pickguard. I think, for me personally, a J/P with pickups in this layout, would float my boat better than a typical P/J does.