Yugoslavia was working well towards this until Tito died. When he died the whole Yugoslavic principles were thrown aside. Mostly because a lack of a strongman after his death.
Plus the whole point isn't a multi-national society, its a Uni-national society. With one Soviet identity.
I know how well Yugoslavia worked during the Cold War. Kind of a sad irony that Bosnia considered itself more Yugoslav than any of the other republics, and yet turned out to be the bloodiest when the federation dissolved.