After Reach, competitive Halo 4 is some of the most fun I've had with the series in a long time.
I've said it before but I'll say it again. For Halo 5 I'd love for cosmetics to be the only unlockable thing in a format similar to this. To clarify, each armor set is a complete set (meaning helmet/shoulders/chest/forearms/legs).
CAREER MILESTONE 1 (unlocked the instant you open the game) - Spartan Armor (primary, secondary, emblem colors, stances)
CAREER MILESTONE 2 (skill rank 5) - Spartan Detail (unlocks Armor Detail, which are your suit's lights, that can be changed to be any color. Also unlocks Under Armor, which you can change from pitch-black to bright white with about 15 gray options in between)
CAREER MILESTONE 3 (skill rank 10) - Visor Color (works like an armor color, you don't have to unlock them)
CAREER MILESTONE 4 (skill rank 15) - Visor Gradients (has Linear, Radial, and Reflection as the gradient options. You choose a primary and secondary color for the gradient to achieve effects similar to the specialization visors in 4)
CAREER MILESTONE 5 (skill rank 20) - Weapon Skins (allows you to alter your primary and secondary loadout weapons. Rather than making individual ones, a universal skin can be applied to any and all of your loadout weapons. These include None, Full, UNSC, Covenant, Forerunner, and Flood. You can change it to any color just like an emblem)
CAREER MILESTONE 6 (skill rank 25) - Weapon Skins Bonus (unlocks more options including Insurrectionist, Heretic, Promethean, and Precursor)
Now for the armor sets themselves, they would be distributed into several categories. Each category has 25 armor sets apiece.
CAREER: Unlocked simply by leveling up or earning Achievements; mostly new armor or modified versions of armor seen in campaign.
COMMENDATIONS: Much easier to get this time. May be artifacts/continuations of relevant armor from past games; getting a grenade commendation would give you Jorge's armor, for example.
SPECIALIZATIONS: These work differently this time around. There are 5 ranks of specialization with varying difficulty; you can enlist as soon as you start the game. They don't give you any perks, just armor. They can be done in any order, though some take longer than others. Class-E specs take one level, Class-N take five, Class-H take ten, Class-L take fifteen, and Class-M take a whopping twenty levels to complete. Halo 4's specialization armors would return here, though likely modified a bit. The format for naming would be something like "Class-M, Spec-X [Rogue]." The Specializations use the alphabet rather than numbers. There is also an elusive Spec-Z hidden on the disc that's essentially the new Recon armor.
LEGACY: 25 sets of notable armor from past games. These would probably include all of Halo 3's, Noble Team, all of Chief's armor variations, ODST + Recon, and so on. I'm not sure how you would unlock these. Probably unlocking terminals, doing SLASO runs, finding skulls, etc.
Note that each set of Legacy armor would also unlock a Stance for use, with you being able to change the weapon used in the Stance to some degree as well.
UPLINK: Pre-order bonuses, DLC armor, and so on.
Armor Skins would likely not return due to the sheer level of armors/color combinations possible. That's a whopping total of 125 complete armor sets.
The lag and connection problems are horrible.
