Saying Jazz pickups on a Fender Jazz bass wired in parallel is a bit
misleading. I take any and all of the Mfg's information at face value. Just like hearing that all Fender 4-string Jazz basses have a L/S set of pickups. I.E 3.625" Neck and 3.750" Bridge.
You will commonly see a Jazz wired like this: http://www.bestbassgear.com/wiring-d...olume-tone.pdf
Incorporating a DPDT switch to toggle between series/parallel is definitely possible and the tonal changes can lend themselves to your style if it fits. Experimenting is totally worth it.
Standard series wiring lends itself to the best output and midrange. Parallel is half the output of Series with more treble and less mids.
For mod's to emphasis and improve your current MIM Jazz I would suggest an aluminum low mass bridge with better saddle and intonation adjustments. A'la Hipshot A-Style. Higher Mass bridge will loose some of that punchy feel a Jazz has. I would also suggest upgrading the pickups to something that caters to you tonally. Nordstrand NJ4SV or NJ4SE would be good choices for the style of music and are both humcancelling. The NJ4SE would be better for the midrange you are working with. You can still series/parallel select them as well. Just my .02