You don't think we need to change ethernet so much as to augment it with a co-processor that handles the "bus" aspect such as detecting when devices are plugged

You don't think we need to change ethernet so much as to augment it with a co-processor that handles the "bus" aspect such as detecting when devices are plugged/unplugged and interrupt handling. Ethernet is just another serial port with higher level mechanisms which handles framing of the data. We just need a little more brains to handle the bus aspect and a simple protocol to talk to devices with as little overhead as possible.