How to Allow Multiple Groups Access to Reviews w/o Nesting

How can Review access be granted to more than one group without having to nest those groups as children of a parent group? 

Example: An organization has 3 project teams, but we would like to only grant access to 2 of those 3 teams. Any combination of 2 teams could be required for a review. We would like to be able to allow access to multiple groups without having to create parent groups for every combination of team collaboration... especially as the number of team combinations increases.