User blog comment:Willbachbakal/Singleplayer Weapons/@comment-3400331-20110223162657/@comment-1330314-20110223221237

There actually was this point where 2K tried to make a system like that, where you could mix weapon and ammo types to make new ones, but it got scrapped. The problem with that idea is that 1) Players would simply combine their favorite weapons and never use anything else. 2) It would be impossible to generate interesting upgrades for every possible weapon combination, both cosmetically and in terms of gameplay. 3) Unless the game reverted to universal ammo, it would be hard to come up with an explanation as to how specially created weapons could fill up on ammunition. 4) The entire thing would be a balance nightmare: for example, you could combine the Machine Gun and Launcher to make a cannon that fires ten heat-seeking missles per second.