I don't know if this would even work but here's my suggestion :
It's a game like TDM, but in the lobby you vote for a default class set-up to use.
It would even the playing fields for everyone and people can't cry that "You have a better gun" or "You used noob tubes" or the unavoidable "MARATHON AND LIGHTWEIGHT BLARGH!"
In the lobby it would say "Vote for next game's class set-up" and it would be selected by majority vote what would be played, if there's a tie all the classes that are tied will be pickable. The set-ups will be picked at random by the game. Guns and attachments are all picked at random. There would be like 5 classes and you can vote for your favorite.
I'm sure no one is really gonna like the idea but it's just a thought on how to even the playing fields. I'm not a developer for the game so I don't really think of all the awesome games but yeah.
Random things : No challenges can be completed unless you have them unlocked. Also if no one votes it will just be a regular TDM and you pick your own classes. Killstreaks rewards won't be affected.