Let's see if I understand:
Batman has the power to investigate people, since there is no godfather, all mafia show up as mafia. He also is unkillable without the Perfect Trap.
Superman has the power to protect one player of his choosing a day and is also unkillable without Kryptonite.
Batman finds Superman then verifies another good player and then the league can be formed.
The Justice League has a minimum of three members but can have more than that.
The Justice League has the power to prevent people from returning from the dead with the Phantom Zone Projector.
If any Justice League member dies then the League is broken and loses the Phantom Zone Projector.
Did I miss anything?
Yeah, you overcomplicated it.
Any townie who has saved up nine points could purchase a Justice League Membership. That could be Batman, that could be Superman, that could be a regular townie. Once any 3 townies have bought a membership, the League is formed and all three members are informed of who else is in the League with them. Since the League can only be purchased by townies, all League members have the benefit of knowing that they can trust each other 100%. (Unless of course Starro is controlling someone but that's a different point). The fact that three townies can form up is the biggest benefit. However, we also gave a side benefit to counteract a few other items/abilities by letting them use the Phantom Zone Projector which helps eliminate possibilites of who could return to the game.
That's all the League is about.
As for UncleBob's question, it was never guaranteed the League would return. We just thought we'd leave the possibility open in case we could see a reason for it since it ended so fast. Personally, I really didn't see how it could be revived or have much intention of bringing it back. I'm not sure if Thatguy was working on any ideas for it but in my mind, it was dead. Congrats on finding a legit way to bring it back. I didn't see it coming.