I think I figured out why the changes were made to my GV. I think someone was trying to bring it close to Modulus Genesis 5 spec. Those came with Bartolini Jazz pickups and preamp. Having never played one I'm not sure how close they came.
I've played one at a local TB'er house here in Colorado about two years ago. The GV's have a basswood body, correct? The Genesis have a graphite spine embedded in wood and have the ergo's of a Jazz bass with a thin neck. My guess is that the previous owner didn't really get in the ballpark and decided to part with it.
Peavey's, like G&L's, are their own thing. I suspect that Hartley didn't want to play second fiddle to anything or anyone. His designs strike me as economical improvements or amalgamations of the best technology available...at the time.