Last Winter I applied for a patent for my idea of a concave neck for stringed instruments and should be officially patented in a month or two.

The obvious improved feature is that when playing a barre chord on guitar, the thumb fits ergonomically better in a concave neck than a round one.
Also, the thumb rides up the side of a guitar neck just as it normally does and doesn't effect existing guitar technique.
The neck design hasn't changed since powdered wigs and I don't mean Paul Revere & The Raiders.