I'm, pretty much, in agreement with ya'. I'm not a huge proponent of sig models, although there have been a few cool ones. I do like the Hellboy, but I'm not interested in getting one.
Having said that, if I do decide to spring for a Z3, I'll probably just spring for a Sklar for a few reasons...
1. Like you, I really want to try Mando frets and the Super Fatties. Plus I think the Sklar already comes with a Detuner?
2. I'll have, basically, 2 years to figure out how to pay for it.
3. If I'm gonna play a sig bass, a Lee Sklar sig would be a great sig to work with.
Other than the NG I had, I can't really think that I've ever owned a sig bass. I DID have a Warwick Stage I Streamer that was built for T.M. Stevens and I currently have a Spector Forte 5 that was built for Kelly Lemieux of Buckcherry, but that's not really a sig bass. I probably WOULD play a Spector Euro 5 Alex Webster sig, but only the non-blood drip version. It's got some killer specs.