I once setup an event in TDU which was similar but more of a hunt. We all grabbed Ford Mustangs (Group F) and went into the city on the east coast (near Lanikai, near the Saleen dealer). The idea was that we setup a boundary around that city that we had to remain in, and we would all turn off our HUD and GPS. One person would start off as the hunter, the rest of us would get a head start and would have to drive around like traffic cars, trying to avoid him.
If the hunter spots one of the other players, he beeps and gives chase. If caught, the person joins him as a hunter, and they both try to get the remaining drivers, until the last one is captured.
It sounds simple, but it does get your heart rate up a little bit when you don't know if the Mustang in the distance is a hunter or not, and you have no idea who you might see when you get to the next intersection.
Unfortunately (for me) we had connection issues at the time, so I couldn't even see what the other guys were typing to each other. I managed to be the last one caught though, so that was alright.
In any game mode where we do chases in TDU1, we always use the 'NFS Host Pursuit III' rules of whether you are deemed 'caught' or not. If you are doing <120kph for more than 2 seconds with a police right near you, or you hit the reset button in the presence of the chaser, you are deemed to be caught. The chaser will honk their horn to tell you that you are busted.
In TDU2, the event hoster could draw the boundary on the map (similar to how you create checkpoints on the map in the Editor). All cars would be the same, but the hunters would have a police car livery. You could force drivers to use the cockpit view for added realism, and you could force the HUD off. You could also restrict who can type message to who in the game, and there could be an option to get notified when someone is caught (or you could leave it off for added suspense). As an added bonus, you could watch a replay of the highlights once the round is over so that you could upload it to YouTube.
I've hosted more 'event' cruises than normal ones, so I'll post more things later on. Feel free to add to the discussion.