Ianto has had so much drama lately I feel like he deserves a break. You can come visit him in the Hub and help feed dinosaurs if you want.
Phanan probably some sort of Wraith shenanagins. Maybe helping him pull an elaborate prank at Hawk-bat base, haven't quite decided yet.
Kanji will have the option of joining him in any of the P4 dungeon levels he's done up to this point, so Rise's strip Club, Mitsuo's game, Naoto's secret base or Nanako's heaven (aka the one with the best soundtrack) You can fight monsters with him or get lost in the maze.
Aigis will have the options of exploring the Dark Hour or Tartarus. Both are creepy, take your pick.