Just to save anyone else the chore of setting different outfits, there's a real easy way to set up for the ALLSTAR LIVES.
Basically, use your three favorite slots for making the best outfit sets for each stat: one Dance, one Visual, and one Vocal. When it comes to the ALLSTAR LIVE, create your sets and then hit Triangle to edit one of the character's outfit for the live. Make sure they have the outfit you want the unit to wear on them, then press Triangle on the first menu (where you can select which part of their outfit you want to change) and confirm on the next window. Hitting Triangle there allows you to set the outfit for all idols in that set but not every idol, which is far faster than going to each idol and setting them up individually.