If you wanted to treat him as his own mob, you could say that the duplicates have the Growing Dread or Uncontrollable Limit, and for each level of the dupe stat he counts as a mob with up to [die step number]+1 dice, using the appropriate Affiliation based on other teammates as the base die size.
So using a d6 dupe power, and using a d8 solo affiliation would let the hero in question act as a 2d8 mob instead of a solitary individual, and otherwise follow the normal rules. Granted, this could turn someone with a d12 dupe and using their d10 affiliation as a 4d10 mob which could get out of hand without one of the above limits.
