Thanks for the feedback guys.

Ive been having further chats with the client on this and it looks like we'll be putting the live feed on hold for now and setting up the system to simply record the driver/passengers in action, the idea being to swop the SSD out of the car when we swop passengers/drivers then play that recording over the projector. though not live after thinking further about it, it does offer some benefits live would not.
theres a few off the shelf setups for this on the market already at very reasonable pricing and from my limited knowledge they would seem a good start point if nothing else.