This... has me a little torn tbh. As a staunch Balor disliker, I can't hate on this.
I absolutely love them finally using the Rumble title matches as the little mulligans they should be used for. We need more Brock Lesnar vs Hardcore Holly type matches.
It's a random pairing... at a time where on the babyface side WWE has two heel champions and... what, three babyfaces right now anywhere close to the main event on the roster? (Styles, Rollins, Strowman if he still counts?). There's plenty of men on the roster who're in the place where Asuka and Becky Lynch were, toiling in obscurity under a painfully stale title scene, but not buried to the point where they can't main event. It's time they start using some of them.
On paper it seems like a can't lose situation for Balor. A competitive loss to Brock probably means more than a win over 90% of the roster... but the Demon is the trump card here. Kayfabe-wise it makes no sense to be regular Balor going into the PPV (but that's no big deal). Demon Balor beating Brock Lesnar is actually an amazing character moment. A Brock win over Demon Balor severely hurts both characters, so that's the direction I'm assuming they're going in.
His size only makes that a bigger deal, but I could buy into someone like Styles or Bryan being able to believably use his size to make it seems like he's fighting from underneath, using his speed and ring IQ to out-wrestle the unstoppable force. Not sure if Balor's the man for the job.