Christian to my knowledge, the other potential Danish candidate to the Polish crown was Prince Carl of Denmark, but he was unwilling to convert. I think Prince Christian would be willing to convert, as he had been candidate for many years, I suspect the unwillingless of the Danish royalty to convert was more to avoid the things in question George of Denmark had zero interest in becoming king, neither had Carl, Sophie Hedevig seem more to have wanted to avoid marriage to the emperor (maybe to keep a potential marriage alliance with the Swedish crown prince open, I suspect if the Danish state had enough interest in the marriage alliance with Austria, she would have converted). A Danish/Oldenburg king of Poland would be pretty interesting, it would give Poland a king without possessions outside Poland, but at the same time access to a alliance network and some access to the Danish armies. Of course if it stay realisitic, I also expect a closer Habsburg-Oldenburg relationship, which could convince Hedevig that the alliance is worth it. Especially if such a marriage help her brother gaining Poland. honestly the real reason was that he was likely gay and had zero interest in becoming king, he mostly stayed out of politics.