There are a lot of JAPANESE people who don't agree with the 14 year old in a Bikini thing, it's not like it's limited to us prudish foreigners. There's a really wonderful feminist woman who's Japanese and writes about problems about Japanese culture and women, problem is, Japan has a very "don't rock the boat" stance on life.
The biggest problem in the way of change is, of course, that the idol industry sells well on what it does now. There's no guaranteeing it would sell were it less sexist, and that's a harsh truth. Even I'm guilty of this as well, I buy at least 3000$ (284,445.98 Yen) of idol goods a year, my collection is huge. I'm still buying up everything their selling to me. Unfortunately, trying to get people to stop buying isn't the answer either, it's punishing the GIRLS for the industry. And we like the girls.