Yea, I had the same idea, with the same name for a site, where they post for bitcoin. Similar to what was on reddit a while ago. Put a QR code on the bikini and people donate if they like it.
To proof if it's really them, people on the site, can ask for a specific pose, as proof.
A perfect opportunity to make some extra money, and you do not have to go nude or semi-nude. Have a age restriction, if you really want to protect under age people from doing this, but they pose on other platforms in any way, so nobody will be able to stop anyone from posting clothed pictures. Site moderators just delete any underage looking pictures, before they are posted on the site.
Have a competition for men too, to make things fair to both sexes.
I think this was frowned on, when it was on reddit though.. but I think that was nude pictures.
Lol, there are loads of bikini pics of me online already anyone can see for free, why would anyone pay to see the same thing?