#4 Mustafa Ali rejoins SmackDown as King Corbin goes to RAW

SmackDown needs more tag teams. Dolph Ziggler and Robert Roode are likely to drop the titles soon to either the Mysterios or Street Profits. The Street Profits don't need another reign so soon, but they will need new opponents. If Mustafa Ali is traded to SmackDown, he can remain a heel.
He can also revisit aspects of his hacker gimmick and align with Sami Zayn. Together, they can further the conspiracy angle while also adding another team to the SmackDown tag team division. It's lacking depth with only four teams at the moment (Alpha Academy would be the fourth team).
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It's hard to know if there will be any NXT additions to SmackDown after Mansoor and Eva Marie were revealed to be joining RAW. At the very least, Ali going to SmackDown gets him away from Mace and T-Bar.
Ali joining SmackDown might conflict with RECKONING (Mia Yim) being quietly moved to the Blue brand already, but they can operate separately from each other. She just needs to show up as her former HBIC character from NXT.
King Corbin's persona has been dead in the water for a long time. He has been booked to lose almost every major feud. It even dates back to his time against Roman Reigns when Reigns was moved to SmackDown. He needs to officially ditch the whole "King" gimmick because he has been the King of nothing over the last year and a half.
Moving to RAW gives him a new start. Even though his prior tenure on RAW was seen as a failure due to RAW's low ratings, it was because he was made the Constable of RAW. The show needed a fall guy and it turned out to be Corbin.
Switching back to RAW as the Lone Wolf or something new would refresh his career. A portion of the WWE Universe might not like Corbin, but he is one of the most natural heels. He is easy to hate and he gets under the skin of fans. That is what wrestling heels are supposed to do.