So your in a game. A player leaves leaving an empty spot in the match.

To fill that spot you invite your friend into the match. Whether this is by inviting to group or by just having it as a seperate option I think this could be a valuable ability to ensure games continue on with a full roster instead of being slowly taken over by bots until it is classified as no longer worth starting a new match.

Sure keep bots as fillers whilst there is no other player. But being able to invite a friend to fill that spot would be a lot more fun since you can instantly have a friend come into your game instead of leaving a good group of players in order to find a new game (if MM would work).