This is a suggestion to a Gamemode i could think that maybe, could be executed very nicely, Raids.
Its how you would imagine a raid, 4 people fighting against a hard boss, what would make it interesting, is giving players custom weapons to defeat those bosses and custom armor, wich we can both do, since sitems is a thing, reviving teammates is also a thing we can already do, wich would boost the team playing aspect alot more, instead of seeing people as score point bags, they are your actual teammates, you need to keep alive.
This is how i would imagine this concept be made:
Every month is a new boss with custom weapons and armor ,designed by the community or wich are based on the season, like Halloween or Christmass.
For everytime you beat one of these bosses with your given moveset, you get a dp reward, or a special item reward like a hat
I want this to be real, since PvE is just boring to grind bosses when you have endgame gear, and when bosses already have high health due to the amount of players, why not make Raids?
I am not that hopefull this suggestion will bring anything but hey, it is a interesting idea to throw around ya know.