It doesn't really negate it's significance, thats like saying that the historical significance of the Tiger II is negated by the fact that we don't have the IS-2, or Pershing.
Right now, nothing we have can challenge it head on, and nothing could challenge it head on unless we went post-WWII, or into prototypes. But the Tiger II doesn't feel the lack, as the other tanks would only serve to highlight it's dominance, by going up against the best the enemy had, and beating it.
So your logic is because we have the Tiger 2, there must be some other tank that can beat it? In the same thinking - we have the 262 so we must add the P-80 to beat it?
Just because Pershings and IS-2's were available does not mean they faced Tiger 2's specifically. In reality the Tiger 2 didn't face the late war lineup you can dream of. T/34-85s, Shermans, Churchill Tanks,
Pershings military record is itchy enough, I proved that a few times you tried to debunk it, it fought in many separate engagements and only 1 squad was in combat. IS-2 is another story, I would favor the IS-1 being added in game which is no way going to combat a King Tiger. It will put up a fight with a Tiger/Panther.
There is a reason the Russians completely ignored the King Tiger - after capturing one they realized mechanically/armor wise it was sabotaged by the workers building it, enough they didn't even bother to lift a finger in attempting to combat a King Tiger, they figure "the few, the broken down" was going to hurt more overall, after all the Russians pumped out hundreds of tanks per one King Tiger. Whether this is the true reason is to be unknown, I support it's probably propaganda, but then again the way the war was going Germany lost it already.
The Panzer III might get added down the road, I hope its not any time soon honestly as it will be a waste of time for those that actually play the game. Only time it would combat right now is the Sherman 75/T34/76 which both would eat it up.
Historically significant? Sure the Panzer 3 holds its place - however for people paying $15 a month, an antique piece of junk won't last 15 seconds in the late war arena.
The Ki-43 however, holds its place in Aces High regardless. Panzer 3? not so much, perhaps once the GV lineups get more completed, then it will serve its purpose in scenarios down the road.