I think what you mean is carbon fiber reinforced composite case.
Anything is possible if you have the money.
Still there is company willing to fabricate for you if you willing to pay.
Still a very mainstream composite.

Like a gimmick too, same like gaming keyboard gimmick.
The reason metal case is nice, because the crispy sound and the feel when typing.
Common metal case in keyboard is aluminum 6061 with addition retouch of surface using anodization.
If you want a more better than aluminum case, you can always go for stainless steel, add a layer of oxide using passivation will be enough.
Damn rich, then go for solid titanium, with passivated layer.

You just love to rub in the gaming keyboard gimmicks do ya? Hahahaha. I poor okay, can't afford custom keyboards now. XD
But yeah, the sky is the limit really. You pay, they make. And thanks for the extra info. Interesting stuff.