I like this project. Any help I can give will be eagerly delivered but most of this is way out of my area.

Some input:
For comms I would suggest WiFi. 11Mbps over nothing but airwaves. Not only can you use it for uploading songs from your PC, but it could also handle the inter-car comms (voice and data) and car to base stuff (for auto cross or start finish line at tracks).

The other thing is touch screen. A 7 inch 16:9 would be my suggestion so that it fits the JDM nav screen enclosure. I realise that's not much use to LHD'ers but it's a nice size for the dash anyway.