I have an American Special Jazz bass with a 9.5" radius. Is it possible to change it to say a 12" or 16" radius without messing up the neck? Has anybody heard of this? My Schecter has a flatter 16" radius that I love death. Or should I just customize a Neck online from Warmouth?
Is it possible, but to do it right means a whole re-fret. I'd suggest selling the bass and buying with the radius you like, or as you suggested, buying a warmoth neck.
Costwise, it would be about a $300 job by most Luthiers. That's assuming that there is enough thickness to the fingerboard that it doesn't need to be completely replaced. Not a big deal to do, technically. The marker inlays/dots may need to be replaced, depending on how thick they are. So, how much is the neck worth?