Now, I'm a bit of a gun nut, and I already love the variety of firearms in this game, but I also really think it has potential for MUCH more out of weaponry. For example, a conversion could possibly be made for weapons by finding a skill book in the mall gun shop, this skill could perform changes, for example, the SMG could be altered to full auto from its current burst fire, and something like the pistol could be altered into a machine pistol.
Next, ammunition, there is already a rather large variety but what if singular weapons were able to be chambered into something else, for example, the pistol or smg could be altered into 10MM Auto instead of 9MM, this could make them do more damage, however are much more innacurate before you get the firearm skills, as your aim is rather unpracticed beforehand.