I’ve noticed that some car models (particular Dodge) are designed such that part of the rear door makes up part of the wheel well. Is this a recipe for early rust?
i dont know but my liberty’s rusty right in front of rear wheel.
Having a rear wheel well is a recipe for early rust. All the salt and water gets flung into the front of the wheel well and just sits there.
It happened on a CRX I used to have, and those don’t have rear passenger doors.
Which is why we should all be driving open-wheel roadsters.
I agree! Caterham, here I come 
Not necessarily. Properly designed and manufactured, it should be as rust inhibitive as any other area of the car.
Find some older models built like this and see what they look like. History is a real good indicator of the future.
Both my 93 Caprice and 2000 Blazer have rear doors as part of the door well. Both are rust free with the occasional wash and wax. I wouldn’t worry about it.
Ed B.