Full disclosure: I don't know diddly about programming. What I do know is that because of various obstacles and limitations of the game engine, certain problems arise when mixing DLCs. For one, you can't make weapons from one DLC be affected by perks from another. So, as an example, weapons that SHOULD be affected by Grunt, like the Red Victory Grenade Rifle, are not. For the collectors edition, it would be nice if the form lists (I'm pretending I know what that means), could be edited to work correctly for all content.