Hello SBS,
If width is an issue, then it has much wider (please excuse the pun) implications than just caravans. Most commercial lorries are wider than virtually all caravans.
There isn't generally an issue with the width of a vehicle as most roads are capable of handling the wider commercial vehicles. Some roads are width restricted or designated as not suitable for commercial vehicles and those restrictions would also have to apply to wide caravans or any vehicle that exceeds the stated width.
Equally we are already used to the slower progress of commercial vehicles, so why single out wide caravans. Again the driver is responsible to ensure the trailer is within the towing limits of the vehicle and any other regulations. So if there is an issue of reduced progress, then blame the driver not the trailer.
If any vehicle has inadequate rear view mirrors then they are illegal, and that is also the fault of the driver, not the trailer.
If the police used powers to stop and confiscate non-compliant vehicles at the point of the offence, then those people who choose to deliberately ignore the regulations would think twice about transgressing in the first place.