I've been down that road - Warmoth don't do any EBMM compatible products.
Reading between the lines, they think they will get sued.
I think they are being overly cautious as a neck pocket is a neck pocket. As long as the headstock was both different enough and not able to be reshaped to match a Ray I can't see any issues.
Bodies are far easier.
I did get an estimate from Shuker about making a chambered body a few years ago - It was just under £500 including it being painted fully and loading the hardware etc. Other household expenses got in the way and now I've sold the bass.
It wasn't going to be an identical shape, a bit thinner as Ray 5's are massively thick, and the upper horn was going to be a little longer to help the balance even more.