I believe, that one can/should just role with it. There's a bit of 'fluff,' if you look at the mission select. The fluff I wanna see, is in the game itself. I don't know about you, but I would rather play against AI with equal measures. Admittedly, I'm saying I'd like it to be normal damage ratios, etc; however, I totally believe that the enemy should be smarter on higher difficulties. Likewise, I think we should get goodies, as well. Power-ups, purchased by score. Such as, say instead of Wraith spawning this round, your MVP happened to purchase a Scorpion Tank drop, the unit equipped with an AI driver, and a turret manned by a marine, both unable to be occupied by the players, for as long as it happens to stay alive. Likewise, weapon drops, including, say, your favorite weapon, like the M90, BR55, MA5, or M7. If this method of purchase for weapon/munition drops was implemented, instead of the round-completion concept currently in place, we might find slightly better results. The game would play, slightly more balanced: sure, Firefight is meant to be tough, but, if an ODST, or in this case, Spartan-II squad, is to hold up, they're of course going to be backed up with enough munition to actually kill the enemy force. As they say, you're not paying for the rounds, but the U.N.S.C. Supply network will ensure you're using them efficiently! Via points... Yeah... That makes sense, right?
Moving on, bigger maps, with better vantage points, and more manageable and generally fun-to-play already Halo maps that are one-sided defense maps, like Higher Ground(Especially,) maybe... If we're lucky, a elongated version of Longshore, actually featuring: a long-shore! Like I thought was gonna be in it. 'Cause, y'know, they said bridge. I thought it might actually have been a cool, multi-staged backwards falling defense!(This idea, might not be bad: hold off the enemy at various choke-points, and when the end of the round hits, all the purchased equipment, soldiers(Yes, marine allies would be a possibly purchase in my mind, a cheaper alternative to a tank, less effective, but may/may not follow you around. If they did that, and, say, followed D-pad issued orders, it might be interesting) move back to the very start, and once more attempt to hold it until the enemy force is eliminated again. This might even make special sniper vantage points, via long Mongoose travel or Hornets/Banshees. It might be fun, you know: actually piloting a Longsword or Pelican. Just once. Maybe those unmanned F-99's, or such, that get controlled via remote control? (Finally! A use for those damn computers that just litter the place.)
Last but not least: role-customization. Allowing you to spawn, with, say, the S2, MA5, etc. Special abilities, as now we're back to Mjolnir Mk. VI and... I think quite possibly IV, the models will have health-packs, which will mean a good reason for a team medic. A slow healer, which any time the combat lulls for more than a few seconds, can heal team-mates. I think various classes, are a possibility, as we can see by the different builds of the Spartans. One, pretty average guy. Big, not too big, just enough to make an impression, another, smaller, obviously a bit lighter, not to mention shorter. One, a full head taller than the average-joe(^.~, Oh, you and I both know, from the beginning you know the end.), another, a marksman, and another, tall and slightly feminine standing Spartan, with, are those combat knives? (I hope to god my Katana might mean something this time around! As Hayabusa should be compatible...) I'd prefer requisitioning to this, but classing yourself in Firefight allows you to know what role you play. I don't like being out in front, I mean, I can do it, but it is is a pain in the -blam!- ass trying to get Endure by myself, and if I could just spawn with a sniper, and requisition my ordinance, I could back-up my one-manned assault, and not have to have eyes in the back of my head, that aren't there. (Back to a wall, or back to a Marine? I'd prefer the latter, and so would Johnson!)