Have you heard of Charachorder?
They are a brand name for "chording" devices.
These devices help you reach typing speeds up to 250 words per minute, without moving your fingers very much.
Each finger switch is like a mini joystick.
The devices are not cheap, but I think they sell the logic boards, or a USB pass-through device, so you could compare 3D printing costs, or wait for under priced copies.
They have a dot com website.