Thanks everyone for the advice so far.
Yes, I think I am in danger of going over the top, but I will explain a little.
I modded an Ibanez RS924. I put DiMarzios (jb +pb), a series/parallel/mute switch for each pickup,a Stellartone bass eleven working over both passive and active (separate switch) options and Volume and Balance concentric pot +three-way toggle.Photos attached
Best sounding bass I ever had but eventually the weight was too much for my elderly shoulder !
I now have a couple of early Warwick Fortress ones, one active, one passive. The passive is the 33rd of the first production run.
This is the one I want to mod; without closing the door on return to orig.
The plan is to put a Warwick three knob preamp with a series/parallel option on a rotary in the fourth hole.
On reflection on the above comments I would be happy with 1) jb + pb both parallel, 2)both series, 3)jb parallel+pb series 4)jb series + pb parallel.
What rotary would do that ?