PVE Warzone

So the general idea is 12 players holding off, whether as a single team or squads against waves of covenant ending in bosses, I don’t see it being too much of a challenge to engineer a gametype for it as everything required is already in place, perhaps maps would have to be limited but that’s already proven possible in Warzone Assault.
Perhaps objectives could be thrown in by way of disarming covenant bombs/jammers/rescuing marines etc.