I have to agree with Blue Flame. Just think of it: In DTM you have got over 50 parts that are mandatory to be used, including among others the gearbox. Moreover, I think it was mentioned in MWM, the German brands buildt their cars with the help of Dallara. It is fair to say that this doesn't make the cars very different, does it?
WTCC's new Super 2000 rules are still around 100bhp realistically (150 officially) away from what DTM engines are capeable, plus from what the Citroen looked like, It won't have too much of this filigree wings etc.