Pak, fausts, shreks or mines (realistically some combination, you won't have the muni for all of it) are a fine soft-counter for t70/stuart. It doesn't make sense for ostheer t2 to be able to hard-counter allied light tanks. Building light tanks is a gamble because they have a fairly narrow window of opportunity and don't have much use in the late-game (stuart especially, t70 recon mode has some good utility). If you give ostheer the ability to shut down allied light tanks as soon as they hit the field that will just push light vehicles back into irrelevance.
the US and OKW both can get their light tank at around the same time they both get decent anti-tank capabilities themselves.
the light tank have 400 hp for a reason. It is to give them durability and longevity in the face of anti-tank.