Is there a way to delay the stream for 30 or so seconds?
That way it would still be close to live, while the spectators couldn't inform either of the playing teams of the opponents movement, thereby limiting the chances of the stream being abused.
If that was possible, the referee could use freelook and the viewers would actually see something.
If the stream can't be delayed, I don't see why a stream from the locked camera-perspective would be a problem.
If the referee follows players and streams that, this would enable ghosting however, so unless the Stream is delayed for more then at least 15 seconds, only the locked camera perspective should be used in my opinion.