FFG definitely has a schedule to balance out the teams, with 3 commanders, 2 operatives, 3 elites, 3 corps, 2 support, and 2 heavies.
Rebels need 2 operatives, probably chewie and either the rogue 1 crew or the Ghost crew, elites in either wookie warriors, Royal guard, or ewoks, hoth troopers, and taun taun rider pair as heavies.
Imperials need another Operative in mayne Krennic or an Inquisitor, death troopers in elites, fleet troopers in corps, and dewback riders in heavy.
Past that, I have no clue what they would do. Add epic models like an ATAT? expand the gane size to finally be at 1,000? Add strafing runs from starfighters?