This would make it so everyone can play the way they want. Think about you could set it so you can only join matches that havent started yet or if you're a guy who hates snipers and shotguns ban them from playing with you. Dont like big maps dont have to play on them, think a guns overpowered dont have to play with it, is there a combo thats overpowered like the Mp40 juggernaut in WAW make it so the two cant be used.
I also think you should be able to filter health like in private matches. Want a high damage weapons so the game plays like MW2 you can do that want lower damage weapons so the game plays slower you can change that.
I would also like to see if this was implemented the ability to add or take away attachments and perks from weapons as well as tweak them. For example some people thought the PP90M1 from MW3 got to much of a bonus from rapid fire so you could lower it to what you want. Lets say you thought quickdraw made snipers to strong take it away from them or maybe you though it just made them ads to fast so you lower the bonus they receive.
Thought the ACR was just a little to overpowered lower its fire rate or damage. Think the SVD is a little underpowered give it the quickdraw handle. People hated the FAL OSW in BO2 because of select fire if this was true you could make it so the FAL couldnt use select fire.
Then I would like it if you could choose how you're connected. In older cods you were connected by location or in BO2 how its based on connection. Make it so you can play with people near your skill level. You could be really specific or be like me and just change dont join matches that have already started and then go play any match.
Lastly of course what ever you change you can only play with people who have done the same. The down fall to that is it will take longer to find and match people with you. The only thing I would want is the ability to set the rank of those you play gainst. I say this because I can see level 80 prestiges setting there opponents to like levels 1-5. It just wouldnt make the game fun for anybody. But of course you can still play against people of higher rank then you if you dont filter anything or use skill based match making.