Any evidence that the austere instrumentation was due to demand of light weight, not because of e.g. limited instrument industry? Or that being a short-range fighter, it did not need extensive instrumentation for blind-flying? As for the fuel gauges, didn't the Hs 129 have engine instruments on the inner side of the nacelles...
Any evidence that its pneumatic systems were troublesome due to being pneumatic? On the contrary, it is very likely that especially in winter conditions pneumatics are easier to maintain and more reliable too. And wasn't the very highly praised M. B. 5 also fully "pneumatic" for reliability and ease of maintenance...