I'm going to start it off with a bang and fantasy book the World Title scene. The WWE needs this advice, I sincerely hope they take it.
I actually had to rewrite this a bit, but the main points remain the same. Reigns continues to act like a tweener while people boo the hell out of him. At Payback he and Styles fight a hard fought match where towards the end there’s a ref bump, Styles accidently catches the ref with a boot while hitting the Phenomenal Forearm. Styles has him pinned but there’s no ref to count. Styles tries to get the ref up then Reigns hits a superman punch. All three men are down when Anderson and Gallows come out. The crowd is going crazy assuming they’re going to attack Reigns and make Styles the champ. Instead, they pick up Styles and hit him with the Boot of Doom. They slide out, Reigns makes the cover and retains. He gives Anderson and Gallows a confused look, then smiles. All three men beat down Styles after the match and pose as the show goes off the air.
On RAW the next night, Reigns comes out with Gallows and Anderson and cuts a heel promo about how the crowd didn’t like him, so he went out and got two of their favorites from Japan, so how do you like him now?. He goes full crazy and calls the group the New Shield. Reigns then calls out Ambrose. He says Ambrose is his brother and he wants him in the New Shield. Ambrose says he still loves Reigns but he can’t support what he did, he can’t join his group. The New Shield brutally beatdown Ambrose and hit him with a triple powerbomb. Styles comes out to make the save and is beatdown too. This sets up the next few months of main event program with Ambrose trying to take down Reigns, but eventually falling to the numbers game, even with Styles help. Styles also gets his chances but suffers the same fate as Ambrose.
After a few months, Reigns is in the ring doing a heel celebration with his New Shield. Ambrose comes out on the ramp with Styles and challenges Reigns to a multiman tag team match where if their team wins, they get a Fatal Four Way Match for the title in Hell in A Cell. Reigns cockily responds that it doesn’t matter who Styles and Reigns find in the back, no one can hang with the three of them. Cue the hard hitting guitar and out comes Seth Rollins. They go down and clear the ring. The crowd goes nuts. When the match happens, Rollins is the equalizer that Ambrose and Styles have been looking for and Reigns is pinned after a curbstomp. This sets up the main event at Summerslam, a Fatal 4 way for the WWE Title inside Hell in A Cell.
Reigns is entrenched as a heel who is actually over, meaning that his eventual face turn will be actually well received. It gives him a reason to turn heel which the WWE has needed for months, but they couldn’t exactly have him join the Authority since they were fighting each other. It gets Ambrose in the main event where he belongs judging by the crowd’s reaction to him and keeps AJ Styles in the main event where he should be for the rest of his career. Anderson and Gallows are also elevated as a clearly dangerous tag team that should be near or on top of the division for years to come. Seth Rollins gets to make his triumphant return where he will clearly get a huge face reaction and you have a huge main event for Summerslam to push buys of the network.
I had written this before Anderson and Gallows had been interacting with Styles. If I had complete control, there would have been no mention of the three and their history before Payback, making their appearance more of a surprise and more of a big moment. Now it seems that Anderson and Gallows will almost definitely be involved in the match in some form, but you can still follow the story the rest of the way and make sure that everyone involved is elevated.