I’m gonna drop in real quick and offer my .02…
I had a Classic 5, and while the neck was slightly wider than any of my customs, it wasn’t any thicker front to back. To me, the Classics are easiest playing Fender-style instruments I can remember playing (maybe with the exception of my Nash JB-5 and its 18mm spacing). To be honest, I really don’t think it’s possible to go any thinner without exposing the carbon rods in the neck.
To compare a Classic neck to the girth of what you get on a Devon is laughable. I’m not being biased here, either. I’ve owned two Devons, and am currently having one built. I ADORE those basses, but those necks are fat compared to any Roscoe I’ve ever played, and I’ve owned almost as many as Shane has.
TLDR: Maybe the problem lies with the player, not the bass?