You can read about this in great detail in the link on my signature. This is basically a chunk of that post put on here! This isn't very organised compared to the other posts i've made in the past but i'm not completely awake yet so I apologise.
Ok, so when I was looking at the Halo 4 forums, I realised that it wasn't just me that wanted to be something other than a Spartan. It has been going on for, well God knows how many years now, that you play as only a Spartan. In very few game modes of the past Halo's you could be an Elite, and that wasn't extremely fun exept for the thought that you're a mighty Elite warrior. I thought what it must be like as a marine or ODST trooper in the front lines of the war while the Spartan goes deep into enemy territory to do gung ho things that are in no way humanly possible. Sure, they are supersoldiers, but I don't like being the star of the show. I like to be the ones that do the dirty work on the front lines. If there were a game mode like firefight (or a campaign for each species) that lets you defend against waves of marines and Spartans and ODST troopers with your other Covenant allies helping you out in a huge battle, (and most of the fighters are AI) that would be a dream come true! You could flip it around and be a marine in a huge battle as well. You could be an ODST that takes a drop pod (after they die) and instead of having a spawn timer, the drop pod fires from high in the sky and lets you choose where to land by steering it around on the way down. The timer would be the time it takes to hit ground. There may be serious glitches or problems with the whole thing, so I don't support this fully.
There should be special abilities for each unit and species. Let's start off with the UNSC. For the Spartan, keep it classic. For the ODST, the drop pod spawn idea. Maybe just choose where you want to spawn and have the regular spawner timer. For a marine, (which is the main purpose of this whole post, cause it's what I want most!) you can do everything a spartan can, exept for assasinating and having shields. They may be weak, but they can have power in numbers and a very low spawn timer! AI would be perfect to have as allies when you are a marine. If you could be a grunt, same story. They have no spawn timer (just a brief second to see what their corpse does) and can't use many weapons. They can access the gunner seat of all vehicles and pilot some vehicles. Jackals can wield some weapons and have a shield that is exclusive to jackals. Jackals can run fast as well. Say, press the LT button to put up the shield. With a skirmisher, make them very fast is all I can say. They are annoying on Halo: Reach. Brutes have no shields (just like all of the mentioned so far) but are invulnerable to assasination and have alot of extra health. Hunters to me is a great idea. Press LT to put up your shield. You can't do anything you can as a Spartan. You should be able to charge with LB and shoot your assault beam that needs a charge up and cooldown with use with RT. Melee with RB. Not much more detail I could go into here.
If there were a game mode that has a ton of AI using vehicles and weapons like any other player does, and they complete objectives (like CTF) like a player, then it could have its own breed of multiplayer gaming. If they were to add a game mode for every accliable game mode on the modern multiplayer, while having its own classic multiplayer section, (say a menu with 2 submenus, AI multiplayer and multiplayer) and then from there it is explanitory.
For the flood, why not use that as the new living dead. Have classic living dead as well because classics are good. If they let you play as the flood and have their own classes like spores and infected marine, and infected Spartan, and so on. It should allow you to be able to spawn instantly as a spore, and let you spawn after 4 seconds as an infected marine. An infected Spartan could take 8 seconds to spawn. They could have varying health levels depending on the class you are. Spores take 1 or 2 shots to kill, marines take 4 to 7 shots to kill, and Spartans take 5 to 12 shots to kill. (headshots are a different story) If a flood spore hits you, you drop dead and then become a flood character on the spot.
If we were to be a marine, we should be able to have full customization of them and change their facial features with a variety of customizations. Let's say: height, fat, muscle tone, skin color (with a logical spectrum of colors), moustaches, eye colors, eye shape (with a couple preset shapes), and head shape.
I spent a decent 2 hours making this. :sorcerer:
Make sure to like this if you like it, obviously. I would appreciate a reply of your opinion on this idea since I didn't consult any other people on what to add and what not to add. I am coming to be around now. I apologise for any errors I made earlier, because I am not proof reading this.