Regarding the PAK43, it seems like a brace option isn't gonna make it through, but how about making it at least not de-crewable prior to the gun itself dying? Similar to Brit emplacements.
That way a single satchel can't nullify it and all you'd have to worry about is repairing it versus healing the crew.
Would it be immune to small arm fire or would it deal damage as if it was a UKF emplacement ?