I think all people should have some ability (within reason) to obtain peaceful methods and information for themselves. I don't think it's a great idea to hand out N/SN to children or people that are in a heavily compromised state of mind (depending on the specific case). But to rather simply not ban or restrict what's needed for someone to make their own decision about this. It would already be difficult for a child or an otherwise impaired decision maker to go about killing themselves from the get-go (exceptions: guns, unique persons), so some speed bumps are already naturally in place (albeit often in a way that hinder rational adults at the moment).
People are already struggling to chug their N/SN here on the forum, sometimes even without having to weigh their suffering against that of bereaved loved ones. SI, family and practical matters of suicide are natural speed bumps that make it hard for most people to fuck around and die without really meaning to do it (again, outliers exist).
For adults with the ability to make decisions for themselves in other contexts (alcohol, smoking, joining the military, etc), suicide should simply be added to the list of available options (i.e, legalize method acquisition and distribution). How this actually manifests will differ depending on how society looks overall in a certain area.
In cases where death makes sense for the individual, even if they are under the age of 18 or not in a rational state of mind, I can see how assistance might be needed. If someone is completely paralyzed, unable to communicate and in constant pain, I don't see how mercy killing is off the table (for an example). A less extreme case where someone is bedridden it then makes sense to meet them half way by giving them the option of a peaceful death, if they want it. Again, how or even if this sort of thing is possible would depend on the society in question.
There will of course be some difficult cases where it's hard to determine what's what, and I tend to err on the side of death when it comes to those.