I do feel that Sailor Moon is a bit of a teeny bopper, but I believe that's part of her appeal. She whines a lot, gets excited over little things, has a jealous streak, loves to eat and go shopping, cries easily, but is a loyal friend that get serious whenever she really needs to. In other words, much of her personality is pretty normal for someone her age, and there's something satisfying about watching her personality mature and develop over the run of the series.
And as for the whole "natural blonde" thing, I agree that seeing a blonde Japanese girl just wouldn't feel natural when it comes to live action (which is why I feel the changing of their hair color during the henshin works well for Pretty Guardian). I don't think Serena/Usagi *has* to be depicted as Japanese anyway if a new version is made; although the original setting is in Japan the creators agree that much of the story is universal and could take place in any part of the world. It also explains why the anime was a success outside of the culture it was originally depicted in.
