I've added this new addition to the "Weapon Loadout" part of each MW2 mission page. Here's an example, found on the Cliffhangar page:
Found in Level
These weapons can be found with and without attachments.
I've only added this format to the Team Player and Cliffhangar pages. I have to confirm and remove some weapons if need be, so bear with me. If you are against me putting this on the pages, comment here.
Also, I think it would be a good thing for each CoD:4 MW and CoD:WaW mission page to have the Weapon Loadout section.