Good
I'd somewhat disagree with you (at least in the strong, repugnant conclusion form of your argument), but this is a much more defensible argument that ones that implicitly rely on the preferences of non-existent people.
at least in the strong, repugnant conclusion form of your argument
What do you mean by this? When I talked about the value of people lives, I was referring to peoples lives, insofar as they have value, not implying that all lives inherently have value just by existing.
Some people see never-existed people as moral agents, and claim that we can talk about their preferences. Generally this means their personal preference in existing versus non-existing. Formulations such "it is better for someone to have existed than not" reflect this way of thinking.
But if the preferences of never-existed are relevant, then their non-personal perferences are also relevant. Do they perfer a blue world or a pink one? Would they want us to change our political systems? Would they want us to not bring into existence some never-existent people they don't like?
It seems that those who are advocating bringing never-existent people into being in order to satisfy those people's preferences should be focusing their attention on their non-personal preferences instead. After all, we can only bring into being so many trillions of trillions of trillions; but there is no theoretical limit to the number of never-existent people whose non-personal preferences we can satisfy. Just get some reasonable measure across the preferences of never-existent people, and see if there's anything that sticks out from the mass.