It sounds like the player/GM have already decided on the character build. That said, you did ask about the value of a limitation "not while duplicated" and "only while duplicated", so perhaps you are still looking into costs... The value of the limitation would depend on how useful the duplicates are. If the duplicates have weaknesses that the primary form does not possess then the limitation for "Only while duplicated" might be higher. It is always up to the GM. That said, (-1) seems about right. Another option (if the GM is okay with it) is to put some powers in a multipower where each of the slots of the multipower is associated with a duplication state of the character.
So... did you write up each Double as having duplication in order to produce each of the "Single"s? ...Or did you write up Quad having duplication (up to 3 duplicates) with "altered duplicates" advantage and having an advantage of being able to generate "Single" at the location of the Double duplicate? This second option seems confusing to me but could work as duplication with the "Trigger" and advantage.
As for new names it would be helpful if you provided a complete write up.... That said, "Combo" for Quad seems like an obvious choice... Perhaps a military reference like "Squad" would be more appropriate, like "The Brute Squad"... just a thought...