That is a very smart solution but the out of pocket cost would probably still be higher. I mean, I don't know the ticket prices or miles conditions, but in the OP's situation only a single coach ticket is bought. The other pax flies "free" in first. I agree it would make the most sense to buy two coach and upgrade both to business. Perhaps there are even enough miles to get one business class ticket entirely for free, buy one coach and have that upgraded to business with the remaining miles. That would be the ideal solution.

Till