#4 Have anyone align with Seth Rollins
From 2019, Seth Rollins was constantly surrounded by others. He led a faction compression of AoP and Murphy. Once AoP were out of action (and eventually released from WWE), the young Austin Theory took up the vacant slot in Seth Rollins' faction.
Austin Theory was phased out of RAW programming, after which he eventually returned to NXT. It's a better place for a Superstar who is years away from hitting his prime.
A large part of Seth Rollins' story in the second half of 2020 was his tension and eventual split with Murphy. While the Australian benefited from being associated with Seth Rollins, it was an alliance that was discontinued.
In 2021, Seth Rollins doesn't need any alliance when he returns. It all depends on which side of the coin he's on.
In his first heel run as a singles star in WWE, Seth Rollins had The Authority's back. He turned face three months after his return from injury in 2016 and spent over three years being a good guy.
A faction wouldn't make sense for Seth Rollins once he returns, nor would any alliance.