The problem with that theory is:
I'm pretty sure George knows who the purchaser of the boat is, especially as it's already in progress and they have 30ish days before the transfer goes through. With the deal already in progress, there is no reason for the purchaser to be there and if he was I'm sure George would have mentioned it, though he's been a bit of knob with info sharing. Surprising us with Mal's presence the day before and Jayes' +1 at the moment of arrival.
Which leads me to the second point, even if it was
him coming as the buyer, George specifically refers to the person as "Jaye's plus one" which means they're together. If it was the buyer, he'd logically refer to them as "Jaye and the buyer" unless he's deliberately trying to set the mc up for a negative reaction.
The only way
him being the buyer scenario can play out is if George is dodgy and setting them up. If that was the case, I highly doubt Jaye would have been willing to go along with it.
The only way it can be
him is if Jaye has brought
him specifically for the purpose of hurting the MC which I strongly doubt. I don't think she's that stupid and that hurt to do so and it would make her irredeemable with probably 90% of the audience. So unless the dev's really hate her and don't want anyone to like her, or have a foolishly misguided sense of their ability to turn it around, I doubt it will be
him.