There should be a licence fee and you could train existing animal control staff so no extra money really would need to be spent hiring staff specifically for people who keep big cats. Most well respected zoos are close to or even in big cities so if the regulations state that the enclosure must be to the level of these zoos then you dont have to worry about a cat escaping.
Im sure there are people with a lot of money out there who would be able to keep their big cats in better and safer conditions than some of the small zoos you find around here. The authorities should make sure that it is only these people who have such funds to build safe and appropriate enclosure and be able to care for their animal that should get them.
White Tiger in Singapore Zoo. U wanna see really good enclosures you should check out this zoo if you ever get a chance. I wish I was living there!