Bring Back Duels!
This is something that may get some initial laughs but before the end hopefully people will like it enough!
There are new people to the game that would benefit from the system of the duels (free shards and fighting practice).
Then there are the veterans of the game that have no time for such menial rewards. But if they bump them up and the difficulty then that would be awesome! We still get duel credits, I just sell mine I don't even use them because dueling a champion isn't enough incentive for me. I gain nothing from playing a simple champion. There are some champions like Emma and IMIW that may require some extra practice for people. So here is my idea!
Uncollected Duels - You have the added benefit of a weekly duel that is tuned up to AW standards. Machoism, Buffet, etc.... Make the matches the hardest champions in the game to fight! The ones that we all know are hard to fight. We all know that Joe FixIt, Spider Gwen, Electra etc.... aren't hard to fight at all. Some good thought went into all the champions mechanics (except Spider Gwen, seriously update the SP1 to something cool). But some enhanced Uncollected Duels for some good rewards for such alliances.
Some of the rewards for milestones could include 4* shards, 5* shards, BC, gold and maybe a new crystal to drop just boosts?
That would be a good start to bring back an old event and make it better for the veterans of the game.