If we are to assume that every non-existent person desires to exist, and that we have the obligation to not block this, then we should be having children whenever possible as to not block anyone.

Sure. This is the philosophical counterpoint to the "Nobody consented to exist so it is unethnical to bring anyone into the world". You spin it to argue everyone has a right to exist and you end up with some sort of neoliberal spin on the Quiverfull movement.

There are people who would say that even if we create good by bringing people that do consent retrospectively, we also harm forcing life into people that wouldn’t and don’t want life.

You're assuming objective standards for "good" and "harm" that aren't a given. And you're still ultimately dictating a choice on behalf of other people - both people who are being born and people who are doing the birthing. I mean, ffs, how do you even approach the idea of consent while intruding on two people in the act of coitus? "Stop nutting! You're violating the potential rights of a potential person!" is a thing you get to say only when you've disregarded the actual rights of an actual person.

not harming is always the priority over giving pleasure

That's a personal ideal, not a functional standard. In practice, people routinely engage in socially harmful practices for the sake of personal pleasure. And that goes well beyond sex. Let me know when we abolish the cruise line industry and then maybe you can come back and discuss chopping off everyone's balls for the sake of potentially existent people.

now that’s called “Benatar asymmetry”

The theory is rooted in the perspective that pain is bad. But even this isn't an objective standard.