Worst Option - Brock Lesnar
Of the worst options, this could be the most likely one to occur. Lesnar holds the briefcase and has mainly focused on Seth Rollins and the Universal Championship. When he finds that he might be barking up the wrong tree, he could turn tail, go away for a few months and return to torment Kingston instead.
Lesnar is one of the biggest stars in the industry and has cross-over appeal due to his career in MMA. Mr. McMahon loves stars with that appeal, even if pushing them comes the expense of other members of his roster. Just ask the women of WWE how they felt during Ronda Rousey's run as Raw Women's Champion. While she was actually more present than Lesnar, the similarities still exist.
The move to Fox might also force WWE to simply book Lesnar to win another title in order to amp things up for SmackDown. I've said this a million times before, but giving him another title run will make the second half of 2019 seem like 2018 or any other time he held a title. We probably won't like it when Kingston loses the title, but some options are better than others. This is one of the worst choices.