I once had, for a brief moment, the idea of creating a custom PCB with mechanical switches as a replacement for the mushy and horrible feeling keyboard of my Smith Corona SL470.

I then realised that I liked manual typewriters quite a bit more (probably a keyboard feel thing), and that PCB design was way beyond my current capabilities, so I promptly parked the idea.

I might revisit the idea at some point, once I muster the courage to learn PCB design.

Other ideas I've had:

Interposer board for smith Corona wedge, to capture key presses (allowing recording of typed text) and/or use the typewriter as a line printer of sorts.
Power supply swap in SC wedge, to allow powering with DC power, and run off of a wall wart or USB power bank (would help make the machine a bit lighter, and more versatile, and removing the power cord that's always in the way)
Smith Corona type bar electric motor swap for a DC motor (brushed or brush less) in the hope of shedding a bit of weight and make it more efficient, and eventually battery powered

These are nothing.but ideas though, and I'll need to do some research before diving in