All Out has Omega/Bucks vs. [insert trio], and the ME is a 4-way for the title shot (vs. Omega) at Grand Slam. Advertise that the fourth entrant will be a mystery revealed on the show (either by a manager/valet, or somebody that REALLLLLY hates Omega struck a deal to get the belt off him).
Omega/Bucks win their match via shenanigans, and make it a point to watch the 4-way match from the front row.
Brian Cage. Hangman. Andrade. Fourth man is revealed to be...
...who goes on to win. Omega flips his goddamn lid at ringside. BOOM. Show feels huge and the PPV audience got their money's worth, too.