Definitely the Tiger Ace, and probably as a very late call-in.
As a call-in, a Tiger I is dangerous. It turns Grand Offensive into better Special Operations, which is the dominant doctrine.
Locked behind three trucks, it's just not worth it. I don't see how it'd ever be better than the two SPHQ tanks you could buy with the resources needed to backtech and call the Tiger.
Plus, it solves it having no skin.
I guess balance team just want OKW do not use tiger replace PanzerHQ,so in 2.0 they give IR44,now give panzer commander but dont want player use tiger with commander too early or repalce T4......
But this change make tiger call in toooooooo late,and why we don't chose KT?
I think tiger ace is best solution,tiger ace can not upgrade panzer commander,and 15cp(or 3 trucks deployed....) is late enough,this two problem will make OKW deploy PanzerHQ for safe.....and reworked tiger ace is very useful unit,I think reworked TigerAce as good as KT