Wow this is fricken awesome, sign me up for the match bro!
Honestly, having us play a match or two, then have him play the replay so he can see ALL participants would be a really cool way to have him voice over for the match.
Having one player's focus is just so limited, and i'm not sure he knows the capability that the playback function has (if it works in beta..i haven't tried it yet).
That being said, we should have a game where he is allied with everyone and shares planetary vision. We also need to ensure no asshats join up.
In this way he won't be attacked and can really have a sweet display of online skills.
I'd recommend a random map because that is the bread and butter of sins multiplayer.