Could have missions that requires that you farm shards to get nto next section of activate something.{COLLECTION}
A mode where a Hero is selected and they have to be protected, catch is that they can only use primary attack.{VIP}
A mode where you have to hunt down targets in a select area. {BOUNTY}
A mode where Heros start in 5 different areas and have to help each other achieve objectives. {COVERT OPS}
A mode where there are bombs that have to be disable in a current amount of time. {Assault}
A mode where one player has to progressively save the others. {PRISONERS}
Just some thoughs of alternative game modes that could be made for the stages.