Why should the clothes not be recycled? I think she did the right thing by using clothes previously worn. Classic clothes should stand the test of time, and the versatility of the coat dress was demonstrated by a change of hat.
I'm afraid I have to disagree with you on this one. I think a lot of thought probably did go into choosing her clothes. It was a classic and elegant dress, that can be used in a variety of engagements.
To me, there was nothing "light-hearted" about the dress. Between the two events at which the coat dress was worn, the "tone" of the ensemble was altered by the hat used. For the christening, there was a happy, almost exuberant hat with flowers. For the commemoration, there was a much plainer and calmer hat.
As W&C settle into their full time roles and undertake a wider range of engagements, I would like to see her go down this route of better utilising her wardrobe, and subtly changing the tone of her outfits by altering the accessories.