I know this may be a bit of a long shot, but I would like some version of a big boss fight. There are a ton of ways to do this, but maybe two teams of 4 vs 1 mega monster. Double the life.
Maybe just a 1v4 as usual, but pre-balanced depending on the statistics of previous games played globally by team and monster. So if you have all DLC characters vs a Goliath, and globally the hunters have been winning 90% of the time, you would weigh the map (new monster map) and environmental (custom monster buff) in the monsters favor to give him a chance. That would be a massive undertaking to autobalance that well, so I wouldn’t hold my breath.
If you don’t like any of those, or it’s too difficult to push through; just the 4v1 boss fight start at lvl 2 no running, or hunting just a real down and dirty boss fight. Possibly a boss fight campaign to add things like minions to help, but additional kinds of minions depending on how bad either team wins, or how many times.
Just spewing out ideas. Let me know how bad you think they are.