Good assessment of the IS-2. I'm glad someone else sees it for what it is. btw... me thinks it would not be any more efficient at killing towns than the other three HE big boys (King Tiger, Tiger, and T34/85). They all three do 234 lbs of damage to OBJ with HE shells. Actually, the IS-2 would be LESS efficient at destroying towns thanks to the horrendous reload.

Also, on the flip side of things I look at what could be/should be added to HTC base on two criteria: First, how does it fit in the AH realm? Second, just what bearing or impact did it have in WWII.
We all can find the gaps in the line up, but which of those missing would actually fair well or find a place in AH? The KV-1 was a Soviet mainstay but in AH it would get walked on thanks to a weak main gun and its slow speed. The Cromwell is fast, has average armor, but has a weak gun (same as on the US M4/75mm), and it doesn't have the Calliope available. The Churchill would be armored well enough, and there are a host of main gun options, but it is slower than a 7 year itch (same category as KV-1).
With the Su-100 HTC would be adding something different and not currently in AH (Soviet TD). New gun, new sights, new platform.
With the Panzer III we'd be adding in a "lessor" medium tank that represents EW and is still very much in the fight in LW. Don't discount the 50mm KWK 39 L/60. Lighter medium tank, new gun.
StuG III = Panzer III chassis and same guns as on the Panzer IV F1, F2, and H. It would be much like the Hetzer, but more "German".