What we did

Our idea was that we used mono-battle rules and played as if you had not selected any unit.  Overseers, observers, 1 queen a hatch, and defensive buildings.  We weren't 100% sure if the champion could expand at all so we did a couple where he didn't and only built macro hatches (with associated queens) or else it wouldn't scale properly.  It didn't change play, but some habits die hard.

Anyways it's not an answer from Sean, but I think it is in good spirit.