Again, for this suggestion, I’m going back to the idea from another game:
How about seasonal treasure hunts where you can pick a piece of loot at the final destination of your choice (like missed set items, for example)? That would be great for those who weren’t lucky enough to get a certain item during a chapter, for example.
This could be nicely combined with the adventure mode to make the way to the goal more interesting, enjoying some additional content on the way to the desired goal.