I've got some ideas for Call of Duty 9, mostly on storyline.
I think the main storyline should be what would happen if one slight moment had changed. If Price had actually killed Imran Zakheav all the way back in Call of Duty 4: Modern Warfare, Price kills Imran, this leads to them not needing Soap, this then leads Soap to become a sniper in a Scottish rebellion as Viktor Zakhaev tried to avenge his father and kill everyone that stood between him and Price, Soap then captures Price and takes him to V. Zakhaev, Zakhaev kills him and there is no need for the S.A.S, and Al-Asad is never stopped, he lands the nuke on the American city, and without Makarov given the word tht this is happening, he is caught in the explosion. Al-Asad is supreme leader of pretty much the rest of the world, and Yuri, Soap, Gaz and Ghost have to take it back on there own. This lonely 4 have to take over the rest of the world.
Now onto the multiplayer:
I think that they should put pro perks into this, here are my suggestions for perks:
Shadows in the night: All enemies are seen on the rader for a short amount of time, once per three times you die.
PRO = Longer amount of time, once every time you die.
REQUIREMENTS = Kill 100 Enemies using this perk
Down and Dirty: You are given the ability to get in a ghillie suit and be completely hidden away, although enemies won't be able to walk on you and that'll be a bit of a giveaway
PRO = Enemies can walk over you, and won't notice you, and you cn also attach yourself to trees without being spotted.
REQUIREMENTS = Stay on the ground for 2 minutes without being noticed (Killed)
Extra Attachment: In game you are given the ability to choose one attachment per gun (even if you haven't unlocked that attachment for that gun) and put it on your gun.
PRO = Depending on the attachment, it gets upgraded, example: Scope gets further range, Flamethrower gets larger surface area, spreads out further. You get the point
REQUIREMENT = To get a specific attachment upgrade, you need to get 250 kills with that specific weapon
That's pretty much all I've got for now, but I might come back with some more.
I'm not sure if you can, but if you can message me if you want more detail into my ideas. Thanks for reading ;D