Apparently one cannot change the outcome of completed story missions without starting a new campaign. If I decide to replay the campaign, will I lose anything, such as weapon unlocks or completed challenges? Can I have more than 1 campaign going? Is there a new game+ mode or something similar to sweeten the pill?
Starting a new singleplayer campaign
call-of-duty-black-ops-2
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Well, I found this on Call of Duty Wikia. I think it covers every single possible outcome for the game (here's the direct link to the image).
The drone that which Section says "We sure as hell don't want that up in the air" or something similiar. It's almost at the beginning near the controllable drone turret when you first go up the stairs on the right side of the map and then enter the large area.
Best Answer
I wondered this myself, I started the campaign over and over by going onto the "new game" option on the main menu. At the time I didn't really care about weapons and challenges, because I assumed that it would be a simple task after Veteran was completed; now that I have done Veteran and have gone through the challenges, I've realised it to be no simple task. In short, go onto "replay mission" and press RB to reset the mission progression. I think by doing this all challenges and guns may still be availabe.
I'd recommend starting a new game on a new profile, doing a challenge or two on recruit and complete the first mission, afterwards go to "replay mission" and see if they stay.
I wouldn't want to lose you tens of hours of play time. I hope this was helpful.