Stalin's death would be seen as a tragedy for the Soviet state by the few people who are interested enough in the early history of Soviet politics to know of the man. He'd be seen as Lenin's hatchet man and his death would mark the end of a balanced Soviet nationality-policy. Were Stalin somehow removed this leaves Lenin (who will still have his stroke anyway) putting someone like Smirnov in Stalin's place, with Bukharin, Zinoviev, Kamenev, and Trotsky as the major contenders.
Smirnov would be both General-Secretary and having a lot of influence with the Cheka so he's a good substitute-Stalin figure who'd simply do what Stalin did and amass personal power and shoot all potential opposition. Albeit with far more of a Zinovievite approach to things than a Stalinist one. A Smirnovite dictatorship, however, may wind up being far more of a co-operation of general-secretary and head of the Cheka/OGPU/NKVD/genericalphabetsoup.
Which might actually wind up with a Cheka that verges into an SS-style state within the state.