I made a consistent case for treating happiness equally, so I don't think there was any straw man involved. I said that I thought your claim was understandable, but I didn't think it was right. Some things can be implicit in our assumptions, even if we don't realise/accept it. The only reason I emphasised nothing was because you mentioned that "no happiness was being deprived", which seemed to refer to the idea that nobody is deprived of happiness in nothingnes. But moving on the the main argument.
Once again, I feel that your statements are limited because they frame things in a biased way. In other words, it essentially says that "nobody is suffering" and "nobody has any need for happiness". However, one could also say:
1. There is a state where nobody is happy, and nobody is saved from suffering.
2. The parent is the only one capable of making the decision whereby a state of affairs of no value (happiness) would turn into one that does possess the positives.
Nothing should compel us to create harms in isolation. However, I do think that the existence of deeply valuable experiences for many gives us a reason to create them. The formation of happiness can certainly be ethical.
I would not say that not creating a person leads to no harm. It could, for instance, severely affect the people who wanted to have a family. However, I won't consider that point here. I don't think there is a valid justification for not creating happiness in a state of affairs that lacked any prior value. Happiness is intrinsically valuable and it is never unnecessary to not create it, unless it leads to greater loss of value, which I don't think it does.
1. If not starting suffering (an intrinsically undesirable experience) is necessary, then starting happiness (an intrinsically preferable experience) can also be good.
2. It's definitely good to do so on behalf of someone who cannot ask for the good themselves.
Furthermore,
4. The happiness can also be deeply valuable and is experienced by many people; it is not insignificant.
5. It is quite precious and is cherished by many people.
I never claimed that life is perfect. However, it isn't an absolute hell without any hope either. Without resorting to angels or demons, there are many people who find joy in seemingly little things, such as reading and gardening. I witnessed this myself due to the time I have spent in a "third world country". Joy can be found in unlikely places, and though it isn't (unfortunately) ubiquitous, at least for now, I do think that it has more than sufficient worth that justifies its preservation. The Eastern tradition also has many other larger beliefs, such as rebirth and the futility of not creating people. However, they also speak of sukkha (happiness) which can be found by minimising unnecessary desires, and I already agree with that idea. Chasing superficial pleasures often leads to harms. I'll return to the main topic now. There certainly is a need to survive, but I don't think that everybody constantly despises it. I, just like many other people, like the process of striving for a greater good, even though I admit that contentment is generally preferable. Again, I am not saying that there aren't hardships, because there clearly are. Nevertheless, I disagree with the idea that their existence always negates the value of the good parts of life. There is happiness, and there is immense resilience in many cases (I remember the genuine happiness in the eyes of the people who came from what many of us would call terrible conditions). It's often a twofold blessing.
When one adds the fact that happiness is being created from a state of no value, I think it would be misguided and unethical to claim that they don't have significance or deserve to be prevented.
If it is good (and not neutral) to prevent damage even if it prevents some happiness, it can also be bad to prevent all positive experiences for the sake of preventing the negatives. I suppose this would also depend on the nature/scope of happiness and harms, but I don't think that it makes sense to say that it's wrong to create happiness if it also creates harms, but it isn't problematic to prevent all good for the sake of avoiding harm. Alternatively, one could say that non-creation is neutral in both cases, but the formation of the positives is still good.
Once again, once one realises the potency that the positive experiences of life can have for a person, I simply don't think that it can be fair or ethical to suggest that preventing all good (which is not-so-simple in every instance) would be preferable.
There could still be harms for those who desperately want to create a person they would care for, but this isn't my main point. I don't think that this is just about harms; it is also about happiness. For existing people, it might be sufficient to not harm them in order to ensure that they live generally good lives. However, nonexistent people are clearly not in a state of affairs they would have an interest in. If creating suffering is "unnecessary", but preventing it is necessary, then I also think that creating a happy life can also be necessarily good. One could also say that it makes sense to care about preventing harms when one exists, but not before it. But I am not taking such a view at this point of time, so I'll move on.
I don't think that this violates Kant's imperative. Nobody has an interest in not existing that would somehow be violated or disregarded by being created. In Kantian ethics, what might be more pertinent would be to ensure that one truly cares for the person and doesn't create them merely because they wish to have more working hands. However, I do think that one actually respects and exalts the dignity of a person by giving them the opportunity to experience goods they would be deeply grateful for and had no way to solicit prior to existing. On the other hand, I don't think that preventing all goods for the sake of a perspective that doesn't sufficiently focus on the goods would be an ethical intention/act.
I would not say that life is always a "gift"; it could certainly turn bad, which is why I support transhumanism and the RTD so that harms can be reduced. However, I think that the value of a gift comes from the overall good it provides, not from just potential harms.
i) The "no-strings" attached might be relevant if greater value/happiness was achievable without causing the harm caused by the negative aspects of the gift. However, it is evident that nonexistent beings don't exist in a state they have an interest in that would be affected by the "inferior" gift. In many instances, it could be a source of inimitable value that, despite its downsides, can still be quite meaningful.
ii) One doesn't have absolute certainty about anything. Everything does involve a certain degree of risks, such as giving a self-help book to someone that ends up making them miserable. Most people do genuinely seem to wish that the person they create would have a good life, and if the taking the risk can be bad, grabbing the opportunity for happiness can also be good. I think that an agenda to prevent all happiness cannot be considered ethical. Weaving the fabric of all happiness can be immensely good. I don't think that most people intend to create harms. If anything, the existence of numerous NGOs and people committed to social causes like charity does show that people do wish to reduce harm. Being happy doesn't have to come at the cost of harms, especially when it comes to different individuals (not to mention that one can also help others in small ways, such as by making a kind remark). For many people, the blessing outweighs the "burden" by a large margin, and intentionally forming that great joy cannot be unethical in any consistent ethical framework.
Overall, I believe that any time one is unnecessarily preventing significant happiness that nobody could ask for or appreciate prior to existing, they cannot claim that they have accomplished an ultimate good by preventing potential harms.