I didn’t read the whole thread but I heard a Rav mention a sale and they specify the total value to be a certain dollar amount. So the got could pay that full amount and take the chometz. I suppose the Jew can demand it too. Unless someone can come up with a clause to get out of it that wouldn’t invalidate the sale.
Keep in mind your goy may not want to do business with you next pesach it you force him.
There may be an issue with say a pizza place that sells his chametz dough. Unlike a normal case where you would be happy to get the full value for your chametz. This pizza store owner does not want to sell his dough for a few bucks when motzei pesach he can sell the pizza and make a big profit. Probably they find a way to work around this or perhaps his intentions don’t matter.