Speaking from experience with a repair on my OB, the fender comes off without removing the door. I had a bunch of work done and the fender had to be replaced, I dropped in one day to see the work in progress (which the shop manager was hesitant because some people don't understand the business and have a panic attack). I wanted to be sure it was being done as it should be (I'm not a body tech but do know enough and know how to spot shitty work). Anyways, fender was off, door still on and being prepped for paint at the time.
The body guys claim this is not a problem and that to get the fender off they have to pull the driver's door and trim pieces and that to get everything to line up again may be difficult.
Bondo is good in winter climates if done right, I wouldn't worry about that.