I have attempted with a Raspberry 3 that acts solely as an access point. I put Plex and nginx webserver on the Pi. I'm able to connect to it with my phone, be able to browse the web server, and open Plex. Unfortunately, the Tesla refuses to connect to the access point. I read that Tesla routes all traffic over VPN to their data center or something, and won't allow connecting to any IP addresses. For example, I set my phone up as a hotspot, had Tesla connect to it, and had the Raspberry 3 (this time acting as a regular wifi client) connect to it also. From my phone, I could access the Pi nginx webserver via its IP address. Unfortunately, in the Tesla, I could not navigate to the Pi's local IP address, nor could I navigate if I put the IP address in a YouTube video.
If anyone has ideas, please offer them up. My intent was to be able to watch video on Tesla screen offline either via Plex or directly browsing to a video file, which are all running off the Pi.