Jon Elson fired this volley in
:

Ah, there are a number of solutions for operator panels, such as USB
and serial, that get rid of the massive cables and dozens of Opto-22
modules.

And if you're just bent on scanning the keyboard yourself, you could use a
matrix instead of a separate input for each key.

There are lots of very simple ways to save on inputs. One 8255 (antique as
it is) could handle hundreds of I/Os, properly arranged.

LLoyd