The Monster Hunter ones are just armour, aren't they? I'm not overly familiar with Monster Hunter, but I've read that a big part of the game is crafting armour from the monsters that you beat, so it seems like there would be other options beyond the two that were Smash 4 DLC.
I'm not sure about all of the ones that didn't make it back, but looking through the list, the ones that stick out are...
-Chocobo Hat
-Geno
-Heihachi
-Lloyd Irving
-Gilgamesh (Tower of Druaga)
-Rathalos Armour
-Blademaster Armour
I'm not sure if there are any other missing Capcom Mii costumes.
I figure that at least two of the three Namco-Bandai Mii costumes are going to return - my guess is that one of those two (Lloyd or Heihachi) is going to get promoted to playable status, while the other one (and Gilgamesh) are going to be brought back as Mii costumes alongside them. Then again, I also figured that we'd have another Namco-Bandai character by now, and that hasn't happened yet.