A) Almost every company will add a "this is shopped" line to their advertisements, which may have a little effect until people get used to it.
B) Models that are more beautiful/photogenic will be the new targets of companies. With the assistance of technological developments in photography, certain companies will be able to gain advantage by pulling a "our lady is not shopped!". They may start doing new researches on how to impress people by changing the angle, background, etc.
C) Again, there is no way you can avoid being mislead by these products. You don't know the model personally, you don't know how she'd look without makeup in real life and when you get used to the new law/system, you'll get back to the point where you've started.
I just don't see how this would be beneficial for consumers. Educating people regarding this issue would be a much more sensible/effective strategy.