Oh yes these threads are very common and im sure that if you shifted through the Soviet Reward units suggestion thread, you would find all of this mentioned.
I will start with the ABSOLUTELY NO stuff:
1) IS-3 & IS-4 DID NOT see any action on the Eastern Front during WW2. The IS-3 was possibly used during August Storm (Soviet Invasion of Manchuria), but we ain't fighting the Japanese we are fighting the Germans. IS-4 wasn't even approved for mass-production until 1948.
2) The Soviets will not have an HMG because they don't really need it, this lack of a Suppresion weapon is their weakness.
Now the Possible: The T-28 could be a very interesting unit to include, but its is very hard to place it into a certain place. I can only imagine it replacing the T-90, mainly because both are AI tanks. One is armed with a Low Velocity HE cannon while the other one is a good armored car-like vehicle. So it might be a plausible thing to replace them with.
The OT-34 (or T-34 with flamethrower) sounds like an interesting tank, possibly a replacement for the T-34 w/ Riders in the Breakthrough Doctrine.
