I'm sure Farage would be a great speaker, but the out brigade couldn't agree enough to come together as a single entity. So the official leave group are variant 1 and he represents variant 2
There are rules that ITV can't breach as the vote approaches, so they will need to be careful, whether they are a private company or not. Given this event isn't likely to happen again any time soon, one would really expect them to stick with protocol.