The sweet spot for a p and a MM overlap - you won’t get a “stingray sound” unless you alter the P sound. And vice versa.
I also built a crazy bass with Two MM pickups, kinda stingray crossed with L1000 - i had 33 different sound options - and active bass and treble and if anything it was too much!
if I were In your situation I would be asking exactly what sound I was looking for - and possibly borrowing or buying then selling a few basses to work out what the answer is before getting the router out. (Or funkles body with the rest of your bass) otherwise it will be very easy to do something irreversible that isn’t what you actually wanted!
and, just cos that sounds like I’m on a downer here’s some things I would love the basses to mod on…
Swap the P for a dark star.
swap for p for a G&L pickup and wire it up like a L1000
Recreate the pickup switching Garry Beers is putting on his basses
Dimarzio relentless neck and middle
A pair of split ‘51 style pickups like Alpher have been doing
A super fat PJ similar to a musicman caprice
Leave thr pickups as it is - it needs a Sadowsky preamp!
Double P setup but reverse middle pickup
Pair of Seymour Duncan New York dual coils
Lace Alumatone PJ setup, just cos Ild like to hear these pickups
Piezo bridge and maybe a ACG-EQ1