The thought has occurred to me - and I wouldn't mind a thumb-trackball on the right hand, either. Design in the physical world is well outside my wheelhouse though - is a keyboard an approachable project for somebody who hasn't done woodworking/machining before, or would I be better served working on smaller projects first?
Totally doable as a first project, I'm midway through building my first keyboard with a large number of modifications and it's been a really fun project. The Dactyl Manuform is a great starting point https://github.com/abstracthat/dactyl-manuform
And /r/ErgoMechKeyboards on Reddit is a great community for understanding what you're trying to achieve.
Personally, I can hardly think of a better first project. The electronics are dead-simple and the hardware is so much up to personal preference that you can just tinker until you are happy.
(I built my first keyboard about 7 years ago as my first foray into 3D modeling and printing. It went well enough that I used it as my main driver until I got a Keyboardio Model 1 years later.)
I 3D printed my keyboard. Sometimes I talk about it on HN and have prepared a fairly detailed email about it because people have follow-up questions that require diagrams. I'm too lazy to put it on my blog, but if you want the details just email me and I can probably point you in the right direction.
Building a keyboard is tedious, but not particularly difficult.
