#2 Best Option: Men's Royal Rumble winner from RAW or NXT
The main names I can think of from either RAW or NXT that could win the Rumble and dethrone Wyatt would be Drew McIntyre or AJ Styles from RAW and Finn Balor or Keith Lee from NXT. Adam Cole would be the biggest star from the yellow and black brand but I don't see him winning a Rumble and dethroning The Fiend. Lee is possibly the biggest physical threat from Wednesday nights who could challenge Wyatt, but the same thought that applies to Cole also applies to Lee.
I'm all for Kevin Owens wining either of the major titles in the WWE, but I think he needs to be the man to take the WWE Championship from Lesnar. For that reason, the three other names that would make sense to me would be AJ Styles, Finn Balor, or Drew McIntyre.
Styles is a made man regardless of if he is a heel or a face. If he stays a heel, he can try to destroy the Firefly Fun House just like Rollins tried to do. The former US Champ could also use the numbers game of the OC to try and get one up on The Fiend.
In terms of McIntyre, he seems like he's just waiting for that one chance to get a shot at a major title. McIntyre oozes charisma and is a legitimate physical threat to anyone. If they want to create a new star who hasn't won a title already, the Scottish Psychopath is more than able. He just needs one chance.
Balor would also work because he was the first victim of The Fiend. They could play on the fact that it forced him to "go back to NXT" if they wanted to. He's likely going to be a part of the yellow and black brand for a while, so it might not happen, but if someone exists that is a logical choice to both challenge and topple The Fiend, Balor would be an easy choice. He's beloved by the fans so there would not be much backlash.