Well the Kv1 was top notch for early war fights. The tank ace Herman Bix had a experiance with a KV1 at 30 meters out, 12 of his panzer 3 rounds bounced off the Kv1, finaly they diabled the tank by knocking out its barrel. The KV1 was very effective in the early war tank battles, I think this would be a great addition to the Early War tank set.
Yes, it was pretty much invincible until '42 when Germans started fielding more powerful guns in their tanks.
It's also worth noting that the Soviet army wasn't really all that happy with the KV-1. It was so slow that more often than not, the T-34 and troops often arrived at the battle before the KV-1 tanks, which were intended to spearhead the attack while the medium tanks like the T-34 would then come in and exploit the holes the KV-1 punched through. They were also so heavy that they would often break the small bridges they had to cross to reach the battle lines. A lot of KV-1 were also not lost due to battle in the early years but because the inexperienced and under trained crews would often abandon the tank when they'd get hit although the rounds never penetrated the armor. Finally, the crews had to be handed picked to man the KV-1.
I don't know if we could add such a beast to the early war set. It would be untouchable, nothing in the early war tank set would be able to penetrate its armor. It would even dominate the other arenas as well because a lot of the problems that plagued the KV-1 aren't going to bother it in the game.
ack-ack