About Secrets & Shadows (the nightsister one), an idea would be to allow players to use their resistance toons in the fight. Sure, thematically, it doesn't make much sense, but:
1. Rey Skywalker (yes that's what I call her, just "Rey" is dumb) is the only GL that cannot be used in any of the Assault Battles. If players knew that Rey could be used, this would encourage some players to spend resources (aka money, gear, crystals etc) acquiring her.
2. This battle is the only one that cannot be beaten by 99.99%+ of players. Has anybody ever beaten tier 3?
3. By adding Resistance toons, they can be used more often and for those players that reliced their Nightsisters and/or Phoenix, it would take nothing away from them.