Well, Supernatural Strength doesn't need to be a minimum requirement. Your Might score must be 6 points higher than the weight of the character they are trying to throw. Although supernatural str gives you a +6, someone with Inhuman Str and a high Might could do it. In fact, someone with a high Might could do it.
An average adult is a +1 Might. So you need Might of 7 or higher. Someone with 0 Might and Supernatural Str would be unable to use another person as a weapon, while someone with 4 Might and Inhuman Str could.
A character
can carry something two levels below his Might
for a short distance (allowing him to make a
sprint roll restricted by Might, with the item’s
difficulty as a border value). He can carry something
four levels below his Might with no real
penalty or can toss it a distance of one zone.
Something six levels below his Might could be
used as a thrown weapon.
Anyways, I'd do it as a spray attack and allow both to dodge. The weapon value would be based on your strength power and an adult is weapon 0. I'd also have them split the weapon value between the two opponents.
No matter how they dodge, you still throw the opponent at the other. A successful dodge by one but not the other means one took the brunt of the hit. Or, if the person being attacked dodges, it just means the one being thrown missed and hit something hard. If the thrown person dodges and the target gets hit, it means the person thrown didn't really get hurt as they were cushioned by the target but the target got squashed and landed on something hard (like the floor, or a piece of furniture. A successful dodge by both means your attack was ineffectual: you threw the guy but he missed the other person and he didn't land particularly hard.
I would, maybe, require the Person to grapple the opponent they want to throw as well.
Weapons would be the skill you'd use to attack. I wouldn't let Might modify since you are already using the power/Might score to determine whether they can pick up their opponent.
edit: I had this exact same issue with a supernaturally strong character who had wings. She'd fly around picking people up and dropping them on others.