Something to compete with the King Tiger??? AH is not socialism, AH can't make things "equal". Use your mind and you can defeat the King Tiger in many ways, young padawan. Try the M18 up the tailpipe, the 1000 lb bird poop, or even the T34/76 HVAP within peein' distance of the King Tiger's flank. In other words, do not think you need a Mike Tyson to defeat a Mike Tyson. Besides, that would be boring.
Aces High does not need any more of Germany's super weapons. It does not need anything per say, but it would be better for game play and historical scenarios, imo, for HTC to look at about 31 different gv's before adding in about the only thing that could legitimately compete with a King Tiger: the Soviet IS-2, and even then it was at best within reach of the King Tiger, not an equal. Sure, some knee jerkers will proclaim that the JS-2 was superior due to late war steel quality, veteran crews, support, etc, but those items are tertiary when comparing gun vs gun and armor vs armor.
StG III, Su-100, Valentine, Crusader, Puma, SdKfz 251/9, Staghound, M7 Priest, Panzer III, KV-1, M3 Stuart, Type 97 Chi-Ha, LVT-4/37mm, Char-B, etc, etc. LOTS of other gv's to think about.