But I would like to see a few better mechanics in the game, mechanics that should have been used since the beginning.
Weapons: Everyone has a favorite weapon, they may not admit it but some people go for look, others go for performance. Make it that their choice is going to make a difference. I would like to see a "Gun Rank System", that the more you use a certain gun the better that gun will become. (no I don't mean it gets stronger) Make it that Play Time with a certain gun makes it so that gun is more useful-- Such as; Unlocking Attachments, Unlocking Camouflage & Ability to equip multiple attachments to that gun. This would make things a lot more interesting, because players wouldn't be breaking their neck to get; "Head shots" or "Kills" in objective games, they would be more concerned about playing the game for fun.
Online Games: Everyone joins a game online once or twice even if they don't like online, well what really makes things hard is when you get a good group, but they start to leave. Implement a penalty system to players that leave a game before it is finished, such as a loss of all experience they gained in that lobby or restriction on joining a new game for x amount of minutes/hours.
Perks: Perks shouldn't be what makes you win at a game, they should be valuable assets that make things more interesting or fun. NOT game breaking. What about players who enjoy the art of surprise? Well tough luck because someone is going to see you and start spraying randomly, and when you think you got an opening to peek out and return fire-- oh snap he has "Slight of Hand" so he finished reloading in 1 second! I will just list all the unrealistic perks; Marathon, (Seriously? You need a perk to run longer then 5 seconds?) Commando, (Who needs a gun when you can knife someone from 15 feet away?) Sitrep, (I can see things through a wall!) Bling, (I can equip TWO attachments, this should be an automatic!) Last Stand, (Oh you shot me 6 times in the chest, I deserve a second chance!) Scavenger, ( That guy using a .50cal?-- these bullets should fit just perfect into my handgun!) Lightweight, (GREAT now that I have this equipped I can run 7% faster then everyone else!) Danger Close, (Yay! Now my grenades are better because I have a PERK!) The perks that I didn't mention are the ones that are slightly realistic.
Killstreaks: Okay, in all honesty this is the biggest problem in ALL(COD) games... You earn 7 kills and you deserve to have a 1.5 million dollar Harrier come to shoot 6 other people! Or you get 25 kills and you call in a Nuclear Bomb! ( This is unrealistic, want to make this more realistic? Give us things we should expect like; a UAV, a Ammo Crate, a Counter UAV... But a Harrier?! Seriously?
Knife: Yes I need a whole section to explain the problem with this mechanic! In no way should a knife be more lethal then a gun. There should be no reason to have players running around with a knife outdoing a player with an assault rifle! Maybe if you made it like a execution where when you knife someone (FROM BEHIND) you slit their throat!-- but knifing someones leg, arm or even chest SHOULD NOT be an instant kill. Nor should you receive experience for it!
Death: Okay everyone dies in a game, but there is no penalty so no one cares about playing it safe, make it that when you die you re-spawn with an empty clip, no I don't mean you have no ammo-- instead you have to reload the gun before continuing your rampage!
Special Operations: AMAZING FUN, if you have a friend that knows how to play the game... Because certain missions in MW2 required a second player-- BAD IDEA! ( You shouldn't have to rely on others to complete something 100%)
Campaign: Only thing that I find flawless in CoD games. You have no perks, you have no radar-- so you can have fun shooting the enemy.(Sure you still instant knife, but how often do you run up to someone with 20 other guys shooting at you?)