Bandwidth of modern digital interfaces would not be a constraint on the amount of data involved in complete control. What would be an issue is the durability of such an interface:
a) it's physical durability to operate in the less than clinical conditions of autocouplers
b) it's ability to operate reliably with some or all of the associated terminal devices under out-of-specification supplies
c) it's ability to operate reliably under quite extreme electromagnetic interference (EMI) conditions and not to suffer electrical failures
Given that any electronic equipment may fail, there would be a need for certain high priority signals to be communicated by hard-wired descrete signals, e.g. braking, power and temperature overload monitoring, especially of equipment directly concerned with the operation of multiplexed buses.