Team Duke. Chief, Joanna, and Big Boss all start off guns ablaze throwing out what they have and doing as much damage as they can. Bryan and Fou-Lu are tanky with Bryan countering fire with the gatling gun and Fou-Lu doing what Fou-Lu does in a berserker rage. Duke provides some fire and rocket launches, but he's even manlier now with the power of AUSTRALIA and bullets avoid his presence and as he strides forward across the box-strewn battlefield. He wants the hot, busty clown woman dancing in the nude on the other side. He goes and grinds up on the sultry, dancing harlequin. He is thoroughly enjoying himself and firing at anyone even aiming at the two of them funny. When he's ready to make this fight into an XXX pay-per-view *poof* Kefka turns back into a creepy naked clown man. Disgusted and enraged, Duke puts a boot through Kefka's head before the clown can do anything, makes him explode, and then fires upon everyone else surviving in the battle without any mercy or hesitation (like he would anyway).
If he somehow doesn't survive (which is an impossibility), KOS-MOS will still be standing with her massive durability. Will she be fighting? Probably not. There are a lot of boxes to check for cheese under.