I know this may not answer your question exactly, but I thought I'd post here anyway because it's related to the title of your thread.
In the winter of 2009 I acquired a used (abused) Corvette Standard (swamp ash body, ovangkol neck, built 14/06/2002). The stock MEC jazz style active pickups were mangled from what I assume was overzealous pounding on the E string (I'm told this bass was a rental for quite awhile), so it really took away from the cosmetic appeal of the bass. The pickups also suffered from the single coil hum noise from lighting etc. which I couldn't tolerate. I was also curious about how the bass would sound with passive pickups.
So, the first item on the list to fix up this poor old bass was to swap out the pickups. I did a little search on the net and happened upon a company called Delano. They make an amazing Jazz style replacement pickup with a cool look I couldn't resist. It's the JMVC 4 FE/M2 with exposed pole pieces much like a Musicman Stingray pickup. They're also passive split coil humbuckers, so I'd be eliminating that single coil noise and adding a true passive option at the same time.
Installation was straightforward (for me), and the bass looks and sounds awesome now. No more noise, and it still has the characteristic Warwick growl. The pickups are hot enough that they even sound great passively.
The bass still has the stock active EQ circuit in it, and I've been contemplating upgrading it to an ACG filter based circuit, but I'm satisfied for now.
Delano also makes a Precision style replacement pickup with the same exposed pole pieces called PMVC 4 FE/M2. Maybe you can try these in combination with the JMVC 4 FE/M2 in your Streamer Stage I. It depends on your taste though. You might not like the look. (or sound?) Here's a link...
Invalid Link Removed
I hope this helps. Anyway, good luck with any modifications you choose.