Not sure if this was suggested already but here goes.

You choose a character to be the boss and have 1 or 2 weaker characters support him/her. For example here is one theme.

Death Star
-Choose a Boss for your team.
Old Ben as the leader/boss with insane stats and maxed abilities.

-Choose the rest of the 3 man team. Have Luke and Leia support Ben at their current level/rarity/gear lvl.

-The battle
Have them fight increasingly difficult waves of empire or just 5 waves of storm troopers before a final battle against the enemy boss.

The end result is a fun endurance challenge with a taste of how godlike your character can become in the future when you eventually max them, or wish to test drive a character you've unlocked. Or just kick a ton of ****