So what is wrong with making profit out of images

Nothing in itself. But, as I said above, I think the possibility of unscrupulous people who are not themselves child lovers, not interested in children relationally, but interested solely in making profits from commercialised 'hardcore' child porn, is a legitimate worry. I do see a potential for exploitation there.

how exactly is someone not consenting to diverse usage by making their images public, without any kind of rights protection?

Well, fair point I guess. But once they are made public, they're public forever. What a child might be happy with at a young age they may well change their mind on later.

I suppose ultimately it's rather difficult to foresee how these kinds of things could operate - we're envisioning a future society which has legitimised adult-child sexual relations, and it's not easy to work out all the specifics from the place we are in now...