Yea, that body is one of the top contenders in this project for certain. I'm not sure Warmoth offers a neck blank, but they offer a blank "paddle" head. However, best I can tell it isn't any less expensive nor does it seem to offer any more wood in areas that may be important.I'd go with the "chunk-o-bass" for your body.
Maybe do the same with the neck.
The least expensive bass neck from Warmoth (that I have discovered) is a maple/maple neck with standard frets (not stainless steel, which I happen to actually prefer). A maple/maple neck with frets installed, and fretboard dots is $180. Add corian nut installed and it jumps to $205. Add a tusque nut and it's $210.
Hmmm .... so I wonder what a stock Squier replacement neck would run, y'know, as a prototyping piece? Perhaps it would be less expensive, y'know just to get the kinks worked out. I know Mighty Mite necks are around $129 with frets and nut installed. That sounds pretty good as a proto part too.
But if this proves itself as a viable thing, I'll probably have Warmoth make me a Padouk neck (no finish required on Padouk, and it feels WONDEROUS in the hand), not sure about the fretboard, and stainless frets. I have several Warmoth guitars (I've assembled eleven so far, the 1st one I ever did was a bass, ironically), and their stainless frets are so nice. They last forever once they are leveled, and on a guitar the more string bends you do the more ~slippery~ the frets become making string bends just that much easier to do.
And ... the Mac Daddy (if this headless thing all works out) will be the double neck headless. Warmoth offers a bass/guitar double neck body. I could easily order it to suit the creation of a double necked Steiny-type shape. It would be so light weight (relatively speaking) and easy to manuever. So I have high hopes for this DIY headless bass trip.
Creating a headless guitar with Warmoth parts is as simple as ordering a Floyd Rose locking nut installed on a stock Warmoth guitar neck, the locking plates work as the headpiece, and install a headless bridge. Headless guitar!
So there's that.