More weapon customisation would be nice

So, people reaching maximum level dont seem to have much more to do. How about giving them some more customisation for the weapons? I’m looking at games like Cod 4 and Modern Warfare, where you can customise the weapons and get different feels for it depending on what you put on them.
You already have it in a minimum, would be nice if you expanded it a lot more. :)

Just a thought to make the game feel more rewarding