That’s interesting! I have a vague memory of a specialist input controller in the 80s which had just 6 (or was it 8) buttons. The user would ‘draw’ a shape representing the letter they wanted to enter.
Another possibility could be a system similar to old mobile phone keypads, where the top-left pad would be used for “A, B, C” depending on whether you tapped it 1,2,3 times.
Not very practical for entering scripts but interesting to think about the possibilities (to me, anyway!)