Sure, you might say it wouldn't be the same child, but life is so chaotic that just from the random decisions you make, any potential child of yours changes wildly day-to-day anyway. That's a million potential children that would choose to be alive, in the time where you could have maybe one. So that's not enough justification. There are lots of good reasons to have children, but you need those reasons, not merely "would choose to be alive".