Im worried about the experience with four player coop on the campaign. The gameplay is definitely fun on it own, but its not like the campaign encourages cooperstive experience.
Many of the events on the map are short contact scenarios for 2-4 players to be engaged in for a while. The enemy count is also really small, and the bosses just seem to be meant for one-on-one duels due to the toght spaces besides the Spartan killers.
I think if players would want a fun and challenging experience cooperatively, the game should increase enemy and enemy vehicle spawns when doing coop. Map is already pretty empty with me solo driving a tank around. And we already have a skull to buff health so we wouldnt need to do anything else. So increasing spawns and spawn rate sounds like the only option.