There are a lot
of characters I'd love as Kreons. Inferno, Sky-Byte, Scourge (ALL of them), Movie Constructicons, Lugnut, Ransack and Crumplezone, Movie Jetfire, Armada & BW Megatrons, Sideways, the Dreads, Lockdown, Terradive, Hubcap, Brimstone, (G2) Dinobots, Straxus, the Pretenders, Seaspray, Cosmos, Rampage and Depth Charge, Slipstream... the list goes on and on.
As for the full Kre-O sets themselves, I'd like to see ones where the Kreon related to the big bot in some way besides being the same character. Like, you build Scorponok and the Kreon is Zarak, or you build the samurai skeleton Bludgeon and the minifig is his inner robot, or you build Soundwave and the Rumble/Frenzy is the little guy.