I totally agree with you , OP.
Surely the minimum requirement of clothes for a woman (or man) doing a serious job is that they cover your underwear and private bits. At the time this happened, Kate Middleton was representing the country on an official tour and was in public, as she knew she would be. With all the time, expense and planning that goes into her wardrobe, is it too much to ask that her clothes should be fit for purpose? It is part of the job to alight from aircraft, including helicopters, and the hazards of these are well known. It is not as if it is the first time - this exact situation, with the same resulting photos, arose before in Canada. Floaty A-line dresses and helicopters just do not mix and it seems perverse that she has not learned this lesson.
The thing is, Middleton knows exactly what royal decorum involves - you just have to look at the long, dowdy, all-concealing clothes she wore before she got engaged to William, when she was still auditioning for the royal role and was nervous of frightening the horses. I think her refusal to conform to basic requirements now she is in the position she wanted is testimony to a steely determination to do things her way, now that she can. The trouble is that by behaving like this ie laying herself open to these photos, she will inevitably be compared to "celebrities" who have made their fame through exposing and exploiting their bodies. This is very bad news for the royal family, who would prefer not to have their future queen featured in a revealing tabloid line-up with Kim and Khloe Kardashian.
As a staunch republican, I view this incident with mild satisfaction as yet another nail in the coffin of an outmoded institution I think we would be better without (along with Charles' public comparison of a world leader with Hitler last week) but for royalists, it's a real cause for concern. At the end of the day, when your job description is little more than dressing well and waving, surely it's important to try to get it right.