I did this recently and at least with two cameras recording when someone walks in front of the stage ( they always do at these shows) and blocks your view you can mix in the edit.
vision mixing is seat of your pants stuff.
anyone see match of the day last weekend when somehow a plane landing from a pilots POV somehow ended up instead of a live interview!
once you sync the audio its much easier.
i sometimes run a third on the audience as an alternative wide shot or to get some applause shots
ttfn
Dave
Maccman Films