Risk of locating it plus the time factor primarily. I live in the rustbelt. I agree it is almost pointless to do major rust repair on these particular unibodies. So you need someone to source the car for you far away. If it is not a driver you also will have to ship it home somehow. There are cars in the salvage yards in the southern states. That are really far better than the cars on the roads here.

As my departed father used to say you can repair the mechanical aspects of any car usually. Serious rust in comparison is another story. I am sitting on a very nice running 240d with fairly low millage. That I will probably part out rather than repair the rust. What southerners call rust is a real lack of understanding. You have to have really dealt with it here at one time to really comprehend the problems. Plus if you do not have serious heat available forget even working on them mechanically. Cancer is a feared term . Yet when using it as a description of the rust problems here it is not an understatement. It kills cars with little to no mercy.