Even if safe, 72V controller x 60V battery x 48V motor sounds ... chaotic. It doesn't sound well thought out. Not well thought out and single track vehicle out among the heathen = unwise. As I understand it, 52V is the dividing line between practical cycling applications and LEV (light electric vehicles). Motorcycles. If the o.p. wants to build an electric motorcycle they are limiting their options using a 'bicycle' motor. I imagine though there is a quantum leap in the prices of components built to LEV standards.