Well said. I think that any kind of situation where the adult would bring baggage into the relationship with a child should be avoided. If your hypothetical world would have adults with the same kind of issues that they have in this one, it may well be the case that the relationship would be a bad idea. I agree entirely. The child should be protected from harm arising from the relationship at all costs.

The girl should experience a loving relationship, or a pleasurable fun interaction with no heavy stuff. If that can't be achieved, best gently and kindly reject her request.

Outside of your hypothetical world, I think that harm arising from baggage, or harm done subsequently upon discovery make the whole thing something to be avoided. I have politely and gently rejected the advances of two girls who I was lucky enough to receive overtures from. I still feel honored that they would trust me with an advance, and will always regret that we live in a world that would make such a relationship harmful to them. But as I said, the girls must be protected at all costs.