Nicholas J. Michalak said:

What really should be fixed is having the cloak lay over the upper chest plate like it's seen in ANH. Like this:

While you are absolutely right, still vader in ROTS has nothing to do with ANH vader. So while thinking placing the cape from the outside, consider the other elements that mus fit that can not be done without reshoots :)

Assuming that vader change his outfit more often than padme during the movies is still an option keep the rots design as way it have :D

-Angel is Iron Man