Coding-wise, it's not possible.
Its not?
Couldn't you add some requirements to the Hetzer Doctrine upgrade, similar to how reward units are unlocked for construction?
Then you'd need a binary requirement for Double AT Efforts, having it unlock with either the Hetzer Doctrine Upgrade or the JPZ IV Upgrade.
Ohhh wait, you can't have two Upgrades in the same Doctrine slot, I see. Yeah, too bad.