Great Ninja War: It'd be nice that in the Great Ninja War that when in battles you'd be placed in a team with the other people placed in the land you're fighting for. The reason I think that this would be a nice little addition is because it's hard to talk and strategize with the two other people you're fighting alongside when everyone is attempting to do the same in group chat.
Arena: There can be some really long Queue times for the Arena and you're stuck in the waiting screen unable to do anything but watch the timer progress. I'd propose that when you've assembled your team and have everything set up, once you press the *on to go into Queue that it treats it the same as when you're waiting for Team Instance. This would allow us to wait however long it'd take until we get into a fight and allow us to interact with other aspects of the game such as going to the Merchants or just moving around the map in general to kill time. I'm personally pretty guilty of going into Queue and just tabbing out of the game only to come back to the end of the match whether it's Victory or Defeat.
Nine-Tails Invasion: As it stands it can be somewhat hard to click on the fox during the event because of the Support Icons. An option to hide them while alive would be a welcomed change (like how you can hide the player list in Sage Battlefield). I can't count the amount of times that when I get up to the boss I end up clicking on Hokage Support instead of going into the actual fight. If this was to happen and you've chosen to hide the icons then when you're defeated by the fox it would automatically unhide so that you can choose to revive, however, once you come back to life it'd instantly revert back to it's setting of being hidden.
Team Sets: So we all know that you can save up to 3 different talent set ups, but what if along with each talent set up you were allowed to save a specific team with it as well? For instance you can have your first saved page as your Fox talents + Lineup and on the second then you can have an AoE set up for Team Instances saved and so on.