Hey, I got some really good news yesterday. On a whim, I contacted Eden guitars about their bass necks. I asked if they could make a Fender spec neck (which they do already) but with an angled paddle headstock. Guess what, they said they could! The prototype is due next week or so. This is exactly what I was looking for as I needed it for my 2+2 design. Their prices are very reasonable and I'll know the final damage after the prototype is finished. A minimum order of 6 is required and I think that's very reasonable too!
So, I'm really looking forward to a standardized neck for my projects. That will make things so much easier and cost effective. More on this as things roll out!