I suddenly wondered to my keyboard (Mine is called Happy Hacking Keyboard aka HHKB)
My keyboard has no print on their keypad.
If you are good at typing, you don't need to worry about any prints on the keypad.
However, everyone makes wrong typing mistakes. But we can't notice the mistakes until we see the mis-type on the screen.
It may not be realistic to give each key a different feel, but I think it would be good idea to at least separate the alphabet and enter key or other functional keys.
I think these problem would occer to blind people as well
I found these kind of keyboards for blind person. But these also doesn't work for the problem.
I can prototype this by making my own keyboard using different types of keys for one keyboard.
https://www.youtube.com/watch?v=omqofEF7kpA
After watching some video in this channel, I like this tangible interface.
As I watched this video, this ball has no feature except pushing. Just looking like feeling of rotation is comfy.
However, I think this kind of interface can have more efficient functions by using these ball.
This device is a portable microphone amplifier. So these interfaces are not necessary to have other functions but these ball interfaces have possibility for describing other interface.