Hi Cappy
Refer to your Strata Management Statement (SMS) the registered document that describes the legal responsibilities of your BMC. Each is a little different depending on which legal firm has drawn up the SMS. There should be a form for either a back up representative or proxy within the SMS. Our SP makes a point of appointing the BMC rep and back up at a General Meeting. We are also looking at the roles and responsibilities of the BMC rep and how we can support them around difficult decisions (read conflict within the BMC) through our by-laws, where our by-laws provide policy guidelines.
The BMC strata manager should also be able to assist with advice around a replacement BMC rep too, regarding the requirements of your SMS.
Hope that helps
Alley Cat