Well, I like this idea.

Often I watch a pure sound video on youtube, and I don't know who is in the car except occasionally when there is a lingering shot on the side and I can read the names. Otherwise, it's "one of the Hyundais" or whatever. If the numbers stayed consistent enough for a casual internet rally fan like me to learn them, that would help.

All we need now is a rule that every car will have a large, clearly visible number on the front so we can see it whilst they are approaching the camera at the start of the (typical) clip.