I'll be humble, I did actually love the cruiser idea as a nice intro for the match, though, I did not like the rest of the game, I personally think (and no offense intended) it's conceptually not original aside from the buying the weapon since it kind of sounds like a mixture between slayer/invasion/Halo Wars with added rules.
When I first glanced over the first paragraph I though your idea was going to be to have a game mode where it would be an endless fight, or an "open battlefield" if you will, where it would be 20 vs. 20, no points or score limit, perhaps time limit for a new game room to start, and as soon one person leaves from either team the game would have room available for 1 person to join thus, and once that new player joins the game he would be dropped from the UNSC Carrier and join. Kind of like just drop and fight.
Good effort though.