It seems that all the 4.2 radiators have the loop for trans cooling (or warming).
I haven't really done any research to see if the C5 S6 manual in the Euro III zone cars had manual trans cooling similar to the allroad or not. If not, then this would be the only OEM radiator I could think of that may not have the trans cooling built in. If it were the case, then you would still need to ditch the afterrun system.
...Although I've seen some specs on radiators with the third outlet on the bottom left that goes to the afterrun pump. I think they may be from C6 or B6 cars, though.
I'm sure it's possible that there may be one out there that would fit, but it would take some research.