You don't see the problem with your "obvious solutions"?
You're not supposed to have all the answers to your problems on a single building. If you want to be able to fight early vehicles better, you go for the mech building in lieu of having a retreat point closer to the area of operations for better map presence and more aggressive infantry play.
Or do you think other players have it all ready in a single building? You have to be able to feel and predict what your enemies are going to be relying on earlygame.
the light vehicle meta is inescapable by this point. Every factions are basically expected to be fielding a light vehicle by about the 6:00 mark. Forcing the OKW to get healing or to get their light vehicle will have pretty devastating consequences.
it's also a more relevant topic for 1v1. Any well coordinated Axis team is going to split their tech. One okw go medical truck and one okw go mech truck, or just have an ost plater build a medical bunker.
In addition, a flak ht buff instead of a raketen/schreck buff means that the OKW will be forced to spend fuel, instead of relying on manpower/munition purchase.