I am not programmer so correct me if I am wrong. When I investigated mission files I found that not so much was controlled by LUA There are dialog conversation, checkpoints and UI mainly. One thing that really disappointed me that you can't control car and characters spawn. It's looks like they was placed manually and then baked to chz file. There is no global variables for every car and character, for every mission there are new local variable that was prescribed in zone file. Also I think that many actions are hardcoded and you don't have any access to them with LUA.