Call of Duty: Modern Warfare 4’s early access beta is giving players their first hands-on with the newest entry in the juggernaut FPS franchise, and while it mostly feels like business as usual, I did come away impressed with one particular change in this year’s installment: smoke. In many shooters, smoke works one of two ways: It’s either close to useless, failing to provide sufficient cover, or entirely too effective, making items like smoke grenades feel mandatory.  Modern Warfare 4…