Let's say that Mikhail Koshkin has a car accident/disease which results in his death in 1936-1937 (or falls foul of the NKVD and gets shot/dies in a gulag around that time) before he could develop the prototypes which led to the T-34, rendering it stillborn. What happens next? What tank do the Soviets develop as an "ersatz T-34", then? How does this affect the Great Patriotic War/Eastern Front?