Not so much for the reason of "non stock" but that it has a "cluttered" appearance. IMHO, if you maintain clean lines, even with modifications, cars just look better, especially, with an MB sedan.
What I mean by clean lines is that when you see a car, you notice the entire car first then a slight change in the grill. With that grill, i'ts all you would see and worse, remember.
(Hint: Make the stars in the grill much, much, much smaller and see if that cleans it up.)