I've encountered this plenty since the release of ODST FF, but it's usually been just the lone gunman trying to ruin everyone's fun or speed past a Challenge. Today I encountered a trio with matching gamertags, emblems, and clan tags. They betrayed each other until there were no lives left and the last one tried to kill me. He met his demise and I was able to report them all, then I begrudgingly finished the wave knowing it would bring them back for them to do it all over again. I was right in the end and the game had to end prematurely due to their tactic. While I don't condone their actions I can see why they would want to get some challenges done as efficiently as possible, I do my best to get most, if not all, challenges done in a quick and efficient manner, even coming up with strategies to tell my friends should they feel inclined to get some more experience and season points. But I do it with good sportsmanship in mind. Never would I end a game early, even if I completed my challenge during the round or set.
As a side note, if they were doing this for a Seasonal Challenge as mentioned above, it would be for Hot Dropper as it is ODST FF only, while Wave Runner can be done in either Reach FF or ODST FF.
Edit: I would also like some kind of vote to kick feature, but it would have to only be made available after a certain amount of suicides are registered, kind of like the Betrayal Boot system. This may be a tall order to fulfill though and may never be implemented, but it sure would be nice. I think for now we'll just have to keep on going the way we have been and report and block these players then hope we don't match with them again in a cooperative game mode.