This has long been my dream TL idea, but I think I'm too much of a perfectionist and would get bogged down way too quickly so I'm just going to have a light discussion on it!
So: after having the Right Opposition and Left Opposition neutered/banned and basically entirely filling the government with his cronies but before Kirov is murdered, what happens if Stalin, say, rather publicly trips on the stairs and snaps his neck? Just doing some research, it does seem like Molotov would be the prime suspect for taking power, although depending on when this happens, Kirov could be a plausible candidate. What do you think? Plus, what are the immediate and long-term effects?