Online (w/ WiiSpeak support) AND offline multiplayer – competitive AND co-op please. That is by far my most desired addition.
Also, some of the ideas of different family members with different strengths sounded interesting, and upgrading your house, too. Not sure I want a spin-off Pikmin tactical strategy game where you develop bases in new areas and such... at least not yet. I still hunger for a meaty, traditional action/strategy Pikmin adventure. And I don't think EVEN MORE pikmin types is a good idea. Five pikmin types is already pushing it, if you ask me. I find myself thinking fondly back to the simplicity that was the 3-pikmin-type system of the original.