Unlike for a general meeting of the OC where proxies are allowed, there is no provision for a proxy for a committee meeting.
However the committee can agree to another owner standing in place of an absent committee member.
As far as standing down goes, neither the OC nor the committee can remove an owner or a committee member from exercising their rights to attend meetings and vote. Only an order from NCAT can do this, but owners cannot under any circumstances be denied a vote at a general meeting ( unless they are unfinancial)