As described above, 4a will not work if the player enters the vehicle.
4b will work.
This is a problem if you want all players have the same EH if entering a vehicle which could have been created from one player (like he bought it in CTI or else) and you want to maybe make an overlay over the radar for deactivating it.
Because it won't synchronize with other players, only the player who created the vehicle has now the EH for the vehicle, but the other MP-players do not.