So as an end game player I miss the usefulness of arena gameplay. So i have a new idea. It’s a random troop challenge that you spend keys to use. You pay 10 keys and you make a team with what troops you would normally get from using those ten keys. Then you fight x amount of battles from pre-made teams or other players teams from same format and try to win. Win x amount of battles get reward. Reward scales with the key chosen to spend. Whether you also would get those 10 items/troops or not could be up for discussion as well.
This sounds like fun - I think you should definitely get to keep the troops if you spend the keys, though!
Like a MTG sealed deck match? Could be interesting