If we're not able to do the full stack, my preference would definitely be toward rosbridge over rosserial. Our comms on this vehicle are ethernet and CAN; I'd prefer to avoid introducing a serial connection.
That said, it might be interesting to revisit rosduino, targeting more capable MCUs. Perhaps ARM with lwip? Mike, what network stack are you running on the M3?
TI provides example code for both lwip and uip, both of which run no problem.
How much of what exists in roscpp would be usable? Or would we be building it up mostly from scratch? I know the protocol is stable at this point, but I have concerns about the long-term maintenance cost of building up and supporting a brand new client.
Mike