#4 It will allow the Royal Rumble to create a new megastar

The connection between Roman Reigns and the Royal Rumble match is what controversies are made of. Reigns has been extremely successful at the event; however, the WWE Universe has not received the big dog’s accomplishments with the same expected enthusiasm.
To set up his clash with Lesnar at Wrestlemania, WWE will opt to take the generic route of Reigns winning his second Rumble match. While that had set up his initial encounter with Lesnar, WWE cannot afford to make that decision again. It proved unfruitful in the past and would be a sluggish attempt by the creative team to ignite this rivalry again.
Cody Rhodes' uncle is a WWE Hall of Famer. More details HERE.
Reigns vs Lesnar at the Royal Rumble would be a unique way WWE could organically set up this feud to conclude at WrestleMania. Therefore, letting the Royal Rumble win go to a Smackdown Live star would be the best possible choice. As stars like Shinsuke Nakamura, Bobby Roode and Kevin Owens are rising hot talent in need of validation. And this open spot could create that spotlight for either one of them.