Don't you already have the Puma? Better than Stuart and available between T2 and T3?
Doesn't stop people from wanting new units. Especially really cool units like the Panzer III. Besides the Puma is a light tank hunter, the Panzer III is a generalist tank / infantry tank, depending on model.
T2 unit with requirement of BP2?
While I like this suggestion, I think it would be too much to ask for. People like Katitof are getting antsy at the idea of it existing at all, let alone non-doctrine. It would fill Ostheer's biggest gap reduce reliance on Commanders. Less reliance on Commanders is always good.