I don't really know of any problem offhand...but...I'd have to assume that if the duty of these parts were interchangeable I couldn't imagine MB spending tens of thousands of dollars to a company for tooling up to pointlessly manufacture another part just to look different than its counterpart.
Personally. I wouldn't be real comfortable switching them. No offence, but you're kind of whitewashing one mistake with another mistake. Save the rear disk for when your rear one goes, it probably won't be long if one failed already, and get the right one for the front.