That's a very interesting though. If every electric car in the world would run a bitcoin full node we would have an incredible powerful dynamic decentralized network. We could actually create a mesh network upon that. EWlon Musk has showed his interest in the blockchain and cryptocurrencies industry through his many controversial tweets & for me it wouldn't be a big surprise if we would actually implement the ability to host nodes or at least integrated wallets. How comfy would it be to make payments from your Tesla touchscreen while on the go instead of using your phone which is mostly illegal?
Yes if they did the mesh as you mention, which Tesla's do not, they use old fashioned mobile data.
If someone were to take
open mesh nodes and combine them with bitcoin nodes, this would be true. Only problem is i don't think wifi works very well while in motion (to each other), parked cars on the other hand...
To make payments you don't need to be running nodes, just put Electrum or similar light wallet. The infotainment is little more than a glorified tablet stuck in the dashboard. Your idea is great but its much easier to just add a raspi or similar device and leave the infotainment alone. Plus you could place it on any car/bus etc. Now you could install a wallet to the infotainment (its Ubuntu in some ARM IIRC) but i'm not sure of the convenience of it. The rear camera could be used to read qrcodes, say at the parking wall (reverse parking).
If Elon gave permission things could go very smoothly.