A bit of preface you can skip if you like; I'm a new player, and loving the game, I think it could use a little love, but I'm plenty happy with it. (Will elaborate on my thoughts on the mixed reception in another thread)
I have one thing I wish I could do in the game, which, would probably be enjoyed by fans of Dungeon of the Endless, but, would contextually be closer to Pikmin 3 in execution.
The ability to tell AI partners in Solo mode to move to a room while in the map screen without needing to switch to them. Perhaps with a light shift in control scheme while the Map is open, such as D-Pad/Not-Aiming Mouse to select a room, and using the command wheel to select a teammate to send to the selected room. This would make Solo Play's handling of multiple characters allow for more flexible strategizing, while maintaining the strengths of the game.