Picture this, if you will. (Prospective custom build!)

[phillipmorephil]

A split-coil p-style at the neck, a MM style in its sweet spot, and a Jazz at the bridge. Controls would be concentric volume and tone for all three pickups, master volume, 3-band preamp on bass horn (think Jazzmaster), and series/paralell switches on treble horn (Jazzmaster again).
It'd be a slightly longer scale, strung through the body.

I'm trying to be versatile tonally, without having to switch basses between songs.

Comments, questions, suggestions?

[napalmito]

Precision and MM pickups will be sticked together, I've got a bass like this. I think the J pickup will be sticked to the MM, so all pickups in one spot will make a strange looking bass indeed

[phillipmorephil]

Well, I was actually thinking about putting the Precision pickup a little closer to the neck, maybe an inch and a half or so. It's like that on my '72 Ibanez Pre-Lawsuit bass, and I like the mellowed-out tones I can get from it.