Well, Barbie is downright wholesome compared to some of the other dolls out there (Bratz, Monster High).
I didn't play with Barbies at all as a kid (just wasn't into them) and I was going to try to avoid them for my daughter (age 4) for all the same reasons that you listed, but then last year she discovered one at a friend's house and had the best time with it. No changing clothes or hanging out with Ken, just carrying her around, taking her to the beach, etc. She started asking for one of her own so finally for her 4th b-day, I got her one, and since then, she's gotten a couple of others from a friend of ours who is a Barbie fanatic (as in, collects them and never takes them out of the box).
Interestingly, she does not play with them hardly at all, now that she has some of her own. She's more into puzzles, building things, art, etc. She also has some Ariel and other Disney princess dolls and they are built the same way.
They do have Barbies in various careers, apparently to show that girls can be anything. Our friend did get us the veterinarian Barbie of course (though I found it annoying that pediatrician Barbie actually looks like a doctor in a white coat, while veterinarian Barbie still looks like a slutty candy striper).
If girls have body image issues, it's not all because of Barbie. You are her first role model - if she sees you obsessing about weight and appearance, talking about being fat or dieting, etc., then that is what she is going to pick up on. The media (TV, fashion magazines, etc.) is a culprit too. If she starts begging for a Barbie and you refuse to let her have one, will you be creating more of an issue than you are trying to prevent?
Right now I am focused on my daughter having a healthy body image by just talking about what are healthy foods that make you strong, and what are sometimes foods that are yummy treats. She also started doing gymnastics last year and loves it, and now is asking to try out ballet. Activities like gymnastics, dance, karate, etc. are all about having strong bodies and being proud of what you can do with them. Girl Scouts could be helpful too. I figure if I've done my job, a Barbie doll is not going to undo all that.
My cousin grew up playing with Barbies and was excited when her own daughter was old enough to have Barbies too. She figured they would play with them together like she used to. Instead those Barbies ended up being driven around in Tonka trucks (her daughter has an older brother) and blown up in army battles and thrown off of buildings. Go figure.