#3 Give King Corbin the Royal Rumble win

Subverting expectations has been a staple of pro wrestling and storytelling for years, and it's a pretty useful storytelling device at times. It is the single biggest factor in Daniel Bryan's eventual WWE Title win at WrestleMania 30 and could be played up again with the right storyline this year.
Think about it! What if WWE were to shock the entire WWE Universe and give King Corbin the Royal Rumble victory? Not only would it leave everyone in absolute shock and anger at what they had just seen, but it would also leave them practically pining for another person to be added to the title picture.
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Fortunately, the addition of a third person to a title match between The Fiend and King Corbin accomplishes a variety of things. The first is that it allows King Corbin to serve a critical heel role in the lead up to WrestleMania. Secondly, it allows fans to slowly get behind The Fiend or whoever else they stuff into the title match.
Finally, it could allow WWE to pull off a triple threat match, which will give the company a chance to take the title off of The Fiend and not affect his undefeated streak. Of course, it will come as a bit of a shock to no longer have The Fiend as Champion, but putting Corbin in the mix could be a great way to give Roman Reigns or someone else the title victory over The Fiend.