There was a fanfic that had Aiden deaged and a former student of Beacon before the events of the game happened. It was a melding of the two canons which was cool but Aiden was too hard to believe as a teenager.
So I thought think about using Aiden's nephew Nicky instead. He's 12 and a blank slate so I thought he'd be easier to send to beacon. And you could develop his relationship with his uncle which is bound to be complicated.
So the challenge is to write a story where Nick goes to beacon under the ID of Fox Alistair. He becomes a part of Team CFVY and puts some distance between him and his old life. Only for his uncle to come back in his life asking his help for a mission.