change my view

What classifies as wanting to die? Would you be in favour of instant death the moment anyone has the thought "fuck I wanna die"? If not where do you draw the line. What exactly does a person need to do, what protections are in place against misuse of the system. How long does a person need to want to die before it's considered valid? Should people in exceptional circumstances be permitted, such as children who have been raped or gone through other trauma.

I find the "messiness" of reality to be logistically incompatible with such an idea

You're not thinking about this from an economic standpoint.

As a child grows, it's body becomes larger, meaning the body will contain more flesh, bones, fat, etc.

Additionally, once the child is fully grown, its cells do not continue to expand in size, meaning there's less rapid cellular division - and therefore less risk of cancer.

Not to mention all the labor it could be forced to do over the course of its life.

No, from a purely economic standpoint, I'd have to disagree. Not only will the summation of flesh increase in quantity (and therefore price per pound), but the flesh will become more stable and therefore more valuable.

Once you add in the value of potential labor, it's of much greater benefit the force a child to live a miserable existence.

Now, if you're talking about children with traumatic brain injuries or other flaws that prevent them from controlling their bodies? Yeah, they aren't going to be worth nearly as much so it's better to use their meat to feed better stock.

Well, there's two things I think you're overlooking.

First is that a child's brain needs time the get to the point where it's realistic for them to exercise their right to death.

While it's debatable whether or not it's good to suspend rights until adulthood, or near adulthood is reached, it is standard practice. Since the concept of informed consent exists, and children do have reduced ability to make informed choices the younger they are, there would have to be a cutoff point of some kind, even if it was lower than most people would find acceptable to begin with.

As such, lifting that suspension of the right to death for children, when it isn't even always accessible to adults that can, reasonably, make an informed decision just isn't practical on any level. So they shouldn't be allowed to exercise that right, at least at present.

The second aspect is that a child cannot reasonably exercise that right by themselves. While it is entirely possible for even very young children to take their own lives, taking it in a way that leaves their organs viable would require adult, medical intervention.

So, the child would be asking someone else to kill them. By any normal standard, taking the life of a child that is not terminally ill would be unacceptable. One can argue that taking the life of an adult in that situation is bad enough, but in order for a child to make that choice, someone is going to have to either lack a conscience, or set all of their principles aside.

Since the person lacking a conscience couldn't be trusted enough to only take part in approved ending of lives, that is an unacceptable option. Since someone that does have a conscience would have to be compelled or outright forced to perform the act, it's not just unacceptable, it's cruel to a degree worse than whatever pain might be caused by refusing an otherwise healthy child their right to death.

I'm sure, based on the body text of your post, that you feel the child should have a right to choose to end their life, and would not be convinced otherwise. So, this comment is directed specifically at the title itself, wherein organ donation is a criteria.

Organ donation requires that the death occur in a way, at a time, that the organs are sustained until they can be removed and transported. There is simply no realistic way to kill oneself that can guarantee that possibility. Even adults that have tried to achieve that goal fail almost universally, and they have to choose means of doing so that a child could not successfully arrange on their own. It's a matter of access and physical limitations. So the only realistic way to do it means someone trained is going to have to do the job. There's absolutely no way around that limitation because once cell metabolism starts shutting down, organ viability fades way faster than someone could be transported to a hospital.

Organ viability isn't even a guarantee when death occurs with medical support on hand, things can go wrong. And even the best EMTs and paramedics out there can only do so much in the field, so the chances are already pretty damn low if you aren't right there in a hospital with all the technology available.

There are also arguments against allowing a child to exercise their right to death that aren't about the practicality of organ viability, but I don't think you really want your mind changed at all, much less about your own pain that leads you to want this option. So I won't waste your time with those.

I will extend the same offer I did in your other post, that if you do want advice or alternate perspectives, I'll give mine. But I'm not going to blow smoke up your ass, or waste either of our times otherwise, beyond also saying that I hope you discover a reason to hope again, and that your life gets better.