I don't think the enforcement would be that much of an issue; it would be among the honors and duties of many a healer, shaman, medicine man, doctor or specialized assistant. I understand your randomization scheme well! And from a "guilt" perspective... it is considered a great honor for a kaishakunin to second a friend's seppuku...

Forgive me if it looks like I'm blurring lines, but these are clearly cultural ones and can be overcome in a matter of a few generations only. Those who can make such a choice for themselves should not be forbidden or prevented to choose such an option. What is more absurd than forcing someone to live through pain and suffering against his will by all means possible?

Yes, you are right, many remain stoic, peaceful, outright defiant and euphoric as they watch the hour approaching. But you used the word stigma yourself. Without doubt, many will still refuse to take the "easy route" or however they may call it - by religious decree or conviction - or plain fear of death, as funny as that may sound.

Others would choose what they deem more dignified for the same or other reasons if they had the option and knew they will not be judged (or not care if), and knew whom to ask for assistance.

And yes, imprisoning people wasn't one of humanity's brightest ideas either :/