With regards to the Tye Zamora bass, it wasn't strictly a signature bass, it was a one-off custom made by one of the Masterbuild team. You couldn't buy it as a model, they won't make you one etc etc. But still, certainly one of the stranger instruments to have 'Fender' on the headstock.
I've owned a couple of signature basses, a Fodera Matt Garrison standard, which was amazing, and a Lakland Skyline Darryl Jones, which was also excellent.
Both of those players had a hand in the engineering of those basses (design, shape, specs etc), although Darryl's was essentially done with A basses first, then Lakland effectively just licensed the shape when Albey started getting more busy as a player.
Si