If you have a look at Rule 29 in the RA-Aus Constitution you will see that it reads: "29. Deleted". This was a conscious decision by those who wrote our Constitution to NOT follow the model rules which, at Rule 29 does restrict the number of proxies that can be held by one member to 5.
You have to remember that the Associations Incorporation Act 1991 seems to have envisaged a club with about 100 members - something like a typical social or sporting club located in one town . So, limiting proxies to 5 and requiring 5% of the membership to call a general meeting make some amount of sense. But, in an organisation with around 10,000 members that is spread across a country the size of Australia, these rules make no sense at all.
The Act in the Aust Cap Territory is very clear and specific about no postal votes. Firstly, changes to the Constitution can only happen via a Special Resolution. For a Special Resolution to succeed, " it is passed by at least ¾ of the votes of those members of the association who, being entitled to vote, vote in person or, if the rules of the association permit voting by proxy, vote by proxy at the meeting." Clearly, no allowance for Postal Voting.
We have postal voting for elections and that is allowable but for a Special Resolution to be passed it can only be voted on by those present at the meeting in person or by proxy. End of story unless you want to move the registered office to NSW which does allow postal voting in its equivalent Act.
I did have a look some time ago about how many rules need to be changed to achieve a reduction in Board Members and it was quite a few. If you reduce the Board numbers to 7 or even 5, trying to maintain some form of Regional representation basis for elections becomes quite silly with a total inequity for the more populous states and a gerrymander for the less populous regions. So, if you are going to change - lets get it right once off.
I strongly agree with Col Jones that the re-write can't just be done and mailed to members 3 weeks before the General Meeting that will get to vote on it. A small group under principles dictated by the Board should draft the new Constitution. The Board should then review it with input from the lawyers and achieve as close to consensus as is possible before it is put to the members for review and comment using the Notice of Proposed Rule Making process. There would need to be information sessions presented in a number of regions like SE Qld, Central NSW, Victoria (near Melb), South Aus near Adelaide and in the West near Perth and in Tasmania. Also, an information session should be held at NATFLY to give as many others a chance to understand and ask questions.
Somehow I doubt Tasmania and WA would ever be ready to give up regional representation regardless of how pointless that is. In the end it just has to get 75% of the votes that are cast in person or by proxy at a General Meeting. This is not an impossible hurdle but it is high enough to make limbo look easier than clearing it.