#3 Getting personal
WWE has done a masterful job of making feuds personal in the past, especially in the build up of previous WrestleManias, and could no doubt do the same thing again in this year's build up to Lesnar and Reigns at WrestleMania 34. In fact, it could create a new wrinkle in their rivalry and get fans invested on a much deeper level.
While WWE has admittedly been hit or miss when trying to make Roman Reigns's feuds more personal, it's hard to argue that Lesnar going around and decimating those closest to Reigns wouldn't create a lot of sympathy for The Big Dog. In fact, if Lesnar were to attack Ambrose while he was recovering in the hospital or at home, it could create a lot of buzz around the match.
Lesnar could then systematically destroy people close to him week after week, which would culminate in The Beast Incarnate going to Reigns's house and confronting his wife and daughter. Not only would all this humanize Reigns to the point of gaining massive fan support, it would also build upon Shield nostalgia to give him a much needed rub.