Best Option - Elias
A better use of McMahon in a title feud would be as an ancillary piece of that feud. Instead of him winning the title, he could abuse his power, just like his father and push one of his buddies to a championship match with the New Day Champion.
Someone who needs a big push to some sort of meaningful title is Elias. He has been aligned with the McMahons since his first night on SmackDown during the Superstar Shake Up. Shane could simply decide to 'reward' him by pitting him against Kingston at some point in the near future.
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While it wouldn't surprise me if Shane took the accolade instead, they need to seriously consider the damage that a McMahon winning the title would do to their company. Elias is already over as a heel or a face, and him cheating to win the title due to interference from Shane would be more believable and better received.
'The Drifter' has already shown that he's ready for a big run at the top. He deserves better than the usual 'performance' angles they do at big PPVs that lead to him getting dropped by returning legends. Creative might think he can recover from those types of situations due to being over with the audience, but that type of booking only lasts for so long.