To make it work I think you'd need a few things...
Because there are so many combinations of I/O what you could do to minimize the number of SKUs would be to create maybe a 1, 2, 4, 6 position carrier board, then single function daughterboards, one stepper driver, one A/D I/O, one thermistor, one low power PWM, one high power PWM, etc. So for an XY stepper with endstop, you run power and CAN to a 2 position carrier and plop a stepper and A/D I/O daughterboard on. For a Z motor, you use a single position carrier. A hotend might use a 4 position carrier, etc.
The other issue is software related... Need to make sure that throughput on the bus is fast enough that a device like an endstop can on one carrier can trigger a motor stop on another in a reasonable amount of time.