I don't think that an act that doesn't go against the interests of an existing person can be an imposition. But if it can be an imposition, then it can also be seen as a genuine gift. A pessimistic imposition cannot devalue the positives.
A few big drops cannot annihilate billions of other ones, even if they are smaller (and here, we are going to simply ignore Mahatma Gandhi, Martin Luther King Jr, Albert Einstein, etc.). If one knows that their action would cause more harm than good, then it would obviously be wrong to go ahead and act in that manner anyway. However, since we don't know for sure, one has to act on the basis of reasonable probabilities. A one-sided assessment that doesn't recognise the power of the positives doesn't seem right. Of course, toxic positivity is also problematic.
The armour can be broken silently. If the "consequences" do not improve/worsen a person's well-being, they cannot be better or worse for someone. Nevertheless, I am willing to accept that they can be bad. But if they can be bad, they can also be good.
The central question was answered but I think that you missed my reply. It's also possible that I wasn't clear enough, in which case I sincerely apologise. As I already said, one has to act on the basis of reasonable probabilities. From what we know, most existing people have an interest in not being pushed without their consent from a plane. There might be a small chance that this person would be terrible sad if they weren't pushed, but since this is highly unlikely, it would be better to not push the person. When it comes to non-existent people, however, one has to keep in mind that they don't have a prior desire to avoid existence that we would be failing to satisfy by creating them. What we do know is that, in spite of everything, the majority of people do seem to prefer existence.
It's only vain if the goal is: "survival of the species for eternity." I disagree with this need for absolute perfection. Just as we don't need suffering to be permanent for it to be better off being prevented, we don't need total happiness for it to possess immense value as long as it can exist. Unrealistic expectations cause unnecessary suffering.
I hope that you have a good day!