I guess it depends on how you define realistic.
In terms of talent and skillset, I think AD is the guy. He has the offensive versatility to accentuate the Jays and also coexist with Rob, and he's a big who can defend in space. I don't know how I'd feel about asking him to check guys like Embiid and Jokic, but there are only a couple of those guys in the league. But there are tons of questions. Can he get healthy? Is his decline in play recoverable, or is he just aging early? Does he even want to play in Boston? Would the Lakers actually trade him, and if so, would they deal a star to their hated rivals - especially without blowing up the rest of our starting lineup in return? So yeah, 'realistic' might not be the word I'd use here.