Diana still photographed well but if you loked at her dispassionately her face was taking on a distinctly pinched look. I don’t think she would have aged well.
As to hats at weddings, what everyone else said, and also that nobody is supposed to wear a dress that outshines the bride’s but the hats are a different matter. And I’m surprised no one has mentioned the traditional millinery rivalry between the mothers of the bride and groom (and gawd help us all if there are stepmums involved as well!).
There’s a charity event here in Boston - the Rose Garden Party - where ladies wearing hats are part of the event. Some people start planning their hats a year ahead of time. Supposedly people do the same thing you do - they have the hat designed first and then find the dress. It’s all about The Hat.
I thought Camilla’s hat looked like bent wheat straw. It took me a second to realize that it was a hat, and that she and Charles had not just been in a hay loft together.