by the way, thinking in terms of other processors that could be used, do you know anyone who has used the esp-32 for 3d printing? it's under $10 and has 32 gpio pins (up to 12 analog inputs), 4m flash, 520K ram, and is a 32 bit processor running at 160/240MHz with wifi and bluetooth built-in. [
espressif.com]
If you are moving away from steppers, you are probably going to move to a custom driver board instead of ramps, it should be easy to add the pads to attach something like this module to it as the brains.