First off, let me say that my daughter wouldn't know what to do with a one-piece -- she's never had one -- as the long torso she inherited from her grandma would certainly make it uncomfortable, initiating the heightened self-awareness and pulling of fabric that the 'cons' in the above debate attribute to midriff-baring styles.
No, I think the larger question is not what swimsuits or any revealing clothes might say of the young girls who wear them but what women -- mothers, especially -- are willing to admit about themselves and the cues children take from all the adults in their life.
And the issue is what we -- the adults -- struggle endlessly to hide: the human body's native (gorgeous) form and function, culminating in sexual expression.
Don't get me wrong: I am not a pageant mom. The makeup and hair products I own fit in a kid's pencil bag (really). I am not a proponent of precocious promiscuity or suggestive clothes styled obviously to gratify the parent, rather than provide for the child's physical or emotional comfort.
On the other hand, I take great pleasure in physical fitness and have found that virtually any article of clothing is more flattering when the flesh it's covering best fits the wearer -- and that holds whether we're talking about women my age with the cheeks to rock a thong bikini or women my grandmother's age, whose capris show off the calves and ankles that can walk mile after mile.
In my house, we try to embrace nakedness as a natural state. I often shower with my daughter and dress without trying to hide my sensual bits -- mostly to save time, but also to hear her questions about the body and development in their native environs. Because she's an only and spends considerable time interacting directly with me, she's constantly evaluating her body alongside mine, rather than her peers'.
I'm sure this has led to more than one of my daughter's teachers hearing about the form my underwear take in comparison to her modest girls' briefs. But it has also resulted in my daughter commenting openly when she recognizes women in the media or on the street "being sexy." For 7, she's remarkably articulate about what she does or does not like about how they chose to dress, and her opinion usually celebrates the human part of the equation, rather than the fabric or the bling on the surface.
It has also led to my daughter observing the work your triceps have to do to execute a decent push-up -- something she's learning in order to catch up with classmates at the local gymnastics studio.
And it has led to inevitable but focused discussion of the privileges of maturing into an adult female. I can wear heels during the school day. She cannot. Some of my attire or activities require me to wear a bra. Hers do not. My body hair requires more maintenance than hers does.
In the end, I want my daughter to be comfortable in her skin -- all of it -- not just the parts that are or are not covered by swimwear. Already, I have no doubt she'll have shoes to go with it.