I was thinking about this recently because as much as I love my Frankenjazz, I don't love it's weight--which at just around 9lbs is not horrible.

I realized that PBG doesn't have any basses routed for P+J pickups...so I'd start there.

Then offer it with a J-style neck (rather than the P-style that all the 4 strings come with now).

...and to make it perfect...

Offer it with a chambered body.

Much lighter weight. Sadowsky seems to think they sound better too.

I would build one of these in a heartbeat.