After the… arguable situation with Evolve, it seems this would be incredibly difficult. Nevertheless, I have a quick set of ideas here.
1v4: This would be still retained in lieu of the whole Evolve aspect, However, unlike in evolve, the 1v4 aspect is instead more akin to Dark Souls, where the Monster Player invades a (full) game server as one of the playable boss monsters, however, this can be disabled for those who really don’t want to deal with it. Also, Destructible terrain.
Class-Specific Weapon Types: Unlike in prior titles, a couple of new weapons are added to the table for only specific classes on top of the already existent weapons,
More can potentially come if I think of them.