Net yet, I just wanted to toss the initial design out to see if it resonated or folks told me I was crazy.
I did think of adding another connector for the PWM motor outputs, that would make this useful for powered units and give you some added functionality.
I may also add a buffer to the serial data as adding serial stuff sometimes overloads the serial line. I'm thinking an op-amp circuit with a 2x gain to give me a nice 5V rail-to-rail serial data stream with more oomph so that it'll drive multiple inputs.