#4 Going for the US Title
If The Miz is synonymous with the Intercontinental Title, then Cena is with the United States Title. He began the 'Open Challenge' gimmick and is obviously the greatest United States Champion in recent history.
Whether he takes on Bobby Roode, Randy Orton, Jinder Mahal or all of them at once, it will not matter. The current US title storyline is based on a 'Top 10' list, which is absurd given that WWE has come up with some interesting storylines in the past. Moreover, the belt has somewhat lost its glory since AJ Styles lost it. If Smackdown really wants to compete with its Monday night counterpart, then they need to fill in the spot which Miz does the best - the midcard champion.
The US and Intercontinental titles have been defended in multi-man matches in the past at WrestleMania unless the creative wants it in the pre-show. There is no other way to continue the tradition than having John Cena in it.