Should we deny euthanasia to old people with brain malformations because they can't understand the beauty of going to parties when they're not depressed due to their disability? What if a kid has a stupid reason for wanting to die but I don't care and I let him do it anyway because I don't want him to experiece the negative things that will inevitably happen to him when he becomes an adult?
I don't see how authoritative answers are forthcoming to questions such as the ones you pose. When people are faced with these sorts of questions they typically have intuitions about the right or wrong thing to do in the specified scenarios, intuitions which vary among people, and which form the basis of the answers they give to the questions. But no moral intuition, or set of intuitions, can be definitively shown to be the right one, which is why all interesting questions in moral philosophy are still treated as open. Individuals' own moral intuitions tend to be inconsistent across cases. Even if there are correct answers to these questions, humans don't seem to have the cognitive abilities necessary to gain access to them in the ways that they can, for instance, gain access to certain empirical and mathematical facts. So we end up being stuck with people devising ever more elaborate arguments to defend their intuitions, which they almost never budge on because, by their nature, our intuitions feel right to us. Hence why the same old moral disagreements go on interminably.
In other words, the thought experiments you offer will persuade almost no one to change their mind about the moral status of suicide.