For certain contactor coils such as siemens, allen bradley, klockner moeller etc there is commerically available coil snubbers that are designed to attach directly to the contactor(for ac and dc), this is a neat and professional way to reduce coil kick, I've used these on a machine that uses very slow pwm via contactors for heating coils, the contactor coils are triggered from a plc's internal relay, and were burning out too quickly.
If you do another prod run maybe you could consider putting all the 415v switching stuff on a separate board.