Two ideas I had for the game

First Idea - New game mode

Game mode 2v8 but with a twist that may make it easier to implement into the game as it stands currently.

There are two trials that take place next to each other in the entities realm and start at the same time. The game mode is 1v4 for both trials but here is where it gets interesting, if the killer manages to kill at least 3 survivors a door spawns or opens on the map that will allow the killer to travel to the other trial that is taking place next door to assist that killer in taking out the rest of the survivors. If there was any survivor in the original trial when the killer crosses over to the only remaining active trial the survivor that remains (if they do remain) has the choice of taking a quick escape and ending their match or moving trials the same way the killer has and support their new survivor team in their quest to escape. 

Killer perspective 

If the killer successfully gets the win in his trial (taking out 3 or more of the survivors) then he is granted the ability to continue immediately in the other trial next door. 

The killer should not be allowed to use his perks and or power when he switches trials to make it more balanced. If the 2 killers can combine for 6 of the 8 survivors being killed then the killers have won (Doesn’t have to say a winner or loser, it can be subjective but killers should strive for 6 or more kills)

Survivor perspective 

If the survivors can stay alive and work well enough to get to the exit gates as a team by opening the exit gate they also lock the killer from being able to help his teammate in the other trial (killer door closes). Once the survivors leave the trial that many of the survivors that escaped count toward stopping the killer from winning (perhaps by them escaping it also gives an advantage to the survivors of the other trial (maybe the first survivor to escape gets the option to risk their life and help the survivors in the other trial). Normal escape options for survivors are still available. 

Disclaimer

The first of the two trials that come to an ending (generators being completed and the exit door opening or the killer managing to get 3 or more kills) gets to interact with the killer doorway. It’s a matter of being efficient if you are looking to get to control the fate of the killer's door.

Explanation

I would be happy with a traditional 2v8 it just would take custom maps or new maps altogether; to build a space large enough to hold the new trials. By having two trials intertwined with each other all maps that are currently in the game are usable and it adds a new feeling to the experience of dead by daylight in this game mode by racing to be the first or first team to decide who has the advantage and the power that could ultimately decide the fate of the match. This also hopefully rewards survivors and killers to be riskier with their gameplay. 

Second Idea - New Killer

The Game Master

The killer has a bunch of notice boards around the map that have an offer that survivors can accept. If that specific survivor accepts the offer they will receive blood points. The team overall receives a punishment to make the trial more difficult. This killer tries to test the survivor's team work and to see which survivors are playing for themselves and want to be greedy. Like a true Game Master, the decision the survivors make will decide how the trial will go. I feel that this is a unique mechanic and adds an element of randomness to the matches. If no offers are accepted the game master will become enraged and will receive his own buffs. 

Specifically, the offer mechanism will look like an interactive board that has some writing on it. whichever survivor clicks the board first gets the blood points and the new punishment is added into the map. Perhaps some offers will just have blood points and no writing so survivors have no idea what is going to happen to their team. Only a certain number of offers can be accepted in each trial.