Linking organic groups - or am I overlooking a better solution?
I have not played around with og much but from what you are saying this should be possible with rules. Basically you would create an event based on the change (perhaps create a group admin role only flag which lets them flag each other to create the bond and the trigger. That way if one breaks the bond, the permissions are reversed which would require an extra but similar rule) that would trigger an action to load a list of users from the group. Then add a loop to loop through the list of users performing an action on each one as you go (i.e. add to other group). Not sure what custom actions og brings to rules or vice versa but I see no reason why it shouldnt be possible this way.