I think it would help the game tremendously if the developers focused more on improving alliance features. Mainly the chat could use a lot of improving, it feels plain and very limiting with the number of characters to can put in a post. This really makes it hard trying to explain things or have a conversation in-game.
It would be amazing if you could be able to challenge other players in your alliance to a match, this could be big for helping to teach newer players how to build their teams, for practice against a set you have trouble facing or just fun in general.
I have mixed feelings about this last one, but maybe being able to trade covers between alliance members? I could see this breaking the game in a lot of different ways though so maybe having to make both players pay a heavy HP or CP fee to be able to trade a single cover to try and keep the game balanced would also be included.