Fine thing would be DLC's collection (I mean: Ratchet & Clank DLC, Ratchet & Clank: Going Commando DLC…. The packs could include new characters , levels ,weapons and (of course) original skins.
Anyway my ideas for skins in All 4 One is:
Ratchet: Classic PS3 (non-comic) Ratchet, Classic PS2 (Old School) Ratchet, Dan, Rusty Pete, The Plumber
Clank: Classic PS3 Clank, Secret Agent Clank, Cowboy Clank, Zoni, Zoni Style Clank (like Zoni Aphelion)
Qwark: Classic PS3 Qwark, Classic PS2 Qwark, Nurse Shannon, Vacation Qwark (Maktar Resort single mingle)
Nefarious: Classic PS3 Nefarious, Classic PS2 Nefarious