people have to remember that, it was untested and this was it baptism of fire, just like the tiger, that had many problem, the Ferdinad, looks to be more of a defensive unit, it would be good for V base defense or Airfield town defense. I rate the Ferdinad a 7 for the things that could have happened to it, the jadgpanther would be a great addition to the game.
The Ferdinand had the same gun as the Tiger with the Porsche chassis that was originally suppose to be the Tigers chassis. It was rather big with a high profile. German doctrine was to have a tank destroyer with the same gun package
as the main battle tank in that class. ie
Tiger-Ferdinand
Panzer-Stug
However this changed a bit when tank destroyers started to be equipped with larger guns,
Jadg Panther had the new high velocity 88 that the King Tiger had
Jadg Panzer had the L/70 75mm that the Panther had
Jadg Tiger had a 128mm naval gun
The Ferdinand played such a small part in German tank warfare that others would be a more obvious choice. These tanks im my opinion wouldn't be good for base defense from the stand point that you had to face what you were firing at. More than 1 target would pose a problem from first locating the target than traversing the tank and then jumping into the gunner position to adjust the gun site on the target and if the target is moving fast it may be out of the gun barrel traverse
before you were able to fire starting this process all over again. The only way I see the turretless tank destroyer playing a part would be in the ambush role that would require very little movement.