I was thinking since the Mantis is confirmed to be in Matchmaking
http://www.343industries.org/forum/topic/14512-ragnarok-and-mantis-trailer/?do=findComment&comment=155800, there should be a mode called 'Prey Mantis'.
What is that you say? A survival game.
Here is how it goes. 1-2 players are randomly chosen to be in a Mantis and hunting down other players in the Mantis in a survival type mode. They can destroy the Mantis' or either hide.
Players that aren't in the Mantis get increased movement speed. Loadouts picked specifically for this game type and no custom loadouts. There will be no place a mantis can't get to places, would be unfair for the player(s) to win the match because someone can't be killed.
Recent ideas:
Non Mantis players will have a Thrusterpack, Active Camo and Regeneration Field to choose from.
Give me your opinions on this, submit your own and thanks for reading!