In order to upgrade you'd need to buy a full fare coach ticket. If it's that important to you than it's worth the extra money.

Air France is a terribly uncooperative airline. I really don't understand their rules for upgrading on codeshare flights with Delta. I've had so many problems with them that I refuse to even fly them anymore. I guess that I'm trying to say that I'm not surprised you can't upgrade on Air France.

My advice is to check flights with Delta out of MCO (since MLB isn't that far away) and see what they can do for you. You might be able to fly DL from MCO - ATL - FRA and then connect to Emirates in FRA.

Good luck!