Connecting separated parts of a keyboard together.

[QuincyJones]

Bare with me here - I'm throwing an idea around in my head about having a modular keyboard. So maybe there'll be the absolute basic keys, and then I'll be able to connect a keypad, a block of additional keys with legends for extra functionality, an F-key block etc.

How can the additional blocks be connected to the basic block? Would some sort of ribbon connector be necessary to connect into the matrix?

[suicidal_orange]

Either you can run lots of wires for the matrix or you can use an I/O expander which only uses 4 wires.  The Ergodox uses one, I'm not aware of anyone using more than that but you can have multiple devices on an I2C connection so it's only a firmware change.

[Findecanor]

If you do use ribbon cables, do make each additional module's logical matrix as close as possible to a square. That way you use the fewest wires as possible.
But an I/O expander uses fewer wires already if the number of keys is larger than 4.

[FrostyToast]

I would use 1u blocks of keys made with Enabler and wire up the diodes and switches so that they can interface with a breadboard.
I think it might be possible and fun but definitely not practical.