They did more than add mounts and shit. They rebuilt the engine entirely. People tend to forget that they practically made a new game because it doesn't seem that different on the outside. That's why the "It's a RE-launch" arguments for why this game should be running flawlessly are moot. You build a new office building...there's bugs in the electrical system, a few doors stick, a toilet or two backs up. A couple of months in there's a critical flaw found in the building's framework or worse there's a fire. The building has to be torn down to foundations and rebuilt. You use relatively the same blueprints to rebuild on top of the old foundations but it's still once again a new building and you're going to have to AGAIN work out electrical bugs and backed up toilets and sticky doors.