Well nta could do some fixes on the source dedi system that mw3 uses(like fixing some password bugs etc).
Also you can use the addon method that it is used now( you insert a plugin dll in the server files e.g promod)
But activision after the 1.7 patch blocked almost every dvar except fov.If in iw5m this client sided blocker can be removed this will be beyond awesomeness