If you're thinking Warmoth or one of the other fancy parts suppliers, I'd think money-wise you'd be a good bit better off getting an already fretless instrument.
You can get a Squier VM fretless for approx the price of Warmoth neck.
If you're looking into it because you don't need the fretted P and you want an engaging DIY project, then go for it!

To me, starting with Squier-type bones, I'd get a fretless neck on the cheap.