The best thing about g+ was its politeness, like Canadians. Although, not real names, someone had to go through an effort to establish an internet identity, and that could be killed by googs if they were bad. As well, you could limit things with circles, but I never used that any more.
So, we need something to eliminate obnoxious trolls and sock puppets. Basically, death threats come from accounts that take two seconds to create, again and again. We need some identity verification, but that could be a nom-de-plume.
Encryption may be the best way to go. You have to create a public and private key and have it registered. That's a big pain, and you can eliminate it being automated. Also, you need to have used that id somewhere.
Canada could host this as a mostly canadabis forum. They could pay for it out of revenue. It would also be used for education, and links to treatment. It would eventually spread to all the drugs we make legal.
ps. Honestly, a raspi3 could host this, with all the people that would join. :)