Your previous post listed also other units, my initial response was mostly referring to those.
OKW does lack early AT though. That was the whole reason why the Schreck got more accessible. The Puma needs to be optional due to OKW's tech system. A usable ATG is also a must for any faction, you can see what issues a lack of penetration causes for USF already. If an ATG cannot deal with even mediums reliably, there is barely any reason to buy it in the first place.
If a unit is doctrinal or not does not matter. Your argumentation was that OKW as a faction has to work without the KT, meaning that building the KT on top will make the build OP. That works for basically all units that are not in the standard build order, including doctrinal ones.
The cost opportunity point is very simple, you can basically boil it down to this: The KT has weaknesses, that you would not have if you'd build something else with your resources instead. Your KT is slow, can be flanked/overrun, not respond to a shifting front line, you cannot rush with it etc. It needs heavy support by the rest of your army, focusing you in one single spot.
Other tanks for example are able to operate more on their own, can be dived to kill artillery etc. That's your cost opportunity, and sometimes the best counter to heavies is not even TDs, but artillery to bleed out all infantry and keep the tanks barely supported. That's the cost opportunity you have. Not even mentioning that I have seen many opponents throw their game because they stalled too long for their heavy.
Obviously all of this is heavily map dependent. On some maps you'll get more benefits, on some others rather the weaknesses.
I said it is noticable, so what is the point?
I assume the reason for the nerf was, that previously TDs were penning 300 armor heavies like the Tiger with close to 100% chance. Basically, a vet3 TD evaporated all meaning of Axis armor. I assume the KT was not really taken into consideration, or deemed to be okay.
You're right having the raketen being not efficient vs medium would be bad for design. But raketen that aren't effectively countered by infantry is also bad for design. The problem with the raketen is its price and usability when associated with heavies and super heavies.
Then I don't understand your comment on OKW not having AT at every stage of the game, the raketen is the only T0 atgun available whenever and whatever you tech. SPshreck just made OKW T2 irrelevant since how you can easily keep at bay light and medium just with the raketen/SPshrek and pfaust until the p4j hit the field.
KT weakness is usually offset by allies and the fact that late game both side have losses. Obviously if you're the only one bleeding and playing badly the KT will not be anymore your free out of hell card. But in the case, and its the majority of situations, you and your opponent are suffering heavy losses and then come the moment to replace them with new units then the KT is simply superior to anything else. Because you don't really need to assess your opponent forces, out of the gate your KT is going to be superior to whatever your opponent would also build or call-in to replace its own losses. So yes maybe in the case your opponent still have a ML20 or Priest/Sexton maybe the KT isn't going to be the best choice but you can still make it so. And any other situation will be KT > all.
This is why I say you can't balance OKW without the KT, if the KT exists and is stock then it means its should be part of any regular build order. As much as the HMG42 or Jacksons.
Because the HMG42 is part of Ostheer their infantry is only 4men squad supposely inferior to other mainline infantry.
Because the Jackson is part of USF late game then USF has shitty other AT and no late game meatshield tank.
Why would it be different for OKW and the KT? Why would OKW be on par with other factions without it if it exist and is superior to anything else?