There is a point where they become so ridiculous that you might as well dress the character in clown makeup.
How can you take a character seriously when their center of mass resides somewhere between the binary stars loosely attached to their chest?
As long as it's proportional to their character as a whole then you'll hear no complaints from me (Baiken from Guilty Gear comes to mind) but after that they stop being "sexy".
A bucket can only hold so much water before you're just watering down everything else.