The head coach in waiting thing, IMO, doesn't really have a big enough sample size to test whether it is successful or not. Kentucky and Florida State are going to be the first that I've really heard of that are going to be using the coach in waiting as their new head coach this year, and that's going to take at least three years to initially evaluate whether it is a success or not.
I guess the NCAA wants to get a beat on it before it becomes a success or a failure. IMO, it's a couple of years too early to think about any rules enforcing what a HCIW can do or cannot. Either way, like I've said earlier, they'll just name it under the table and tell the recruits who the coach in waiting is. If a recruit spills the beans, I could just see the school saying, "Nope, we didn't say this to that kid".