You might want to take a look at some of my hat patterns:
Three of the hats are ribbed adn all of them have plenty of decreases in them.
The key is to just work the decreases where needed and work the rest of the stitches normally. Don't try to make every row 2x2 ribbing, just let go of the fact that you will have evenly spaced stitches that are out of pattern. As you work the decreases, they will just blend in and look fine.
Since i don't know your gauge or how you are working your decreases, I can't really work the whole thing out for you, but I do recommend practicing on a swatch to see what happens. You'll think it looks bad at first, but after you bind off, you'll see that it's fine.