An adjustment of this order of magnitude will inevitably impact on the rand, but it is not clear whether under these circumstances the rand would find itself moving with the dollar, or in the opposite direction. Much will depend on how world growth and risk perceptions are affected in such a scenario.
Nevertheless, it is not an insurmountable problem. It is possible to build and respect Chinese walls between decision making for monetary policy and decision making for financial stability. In the US for example, the FOMC (Federal Open Markets Committee) is responsible for monetary policy decisions while the Board of Governors of the Federal Reserve is responsible for financial stability decisions.