Re: None of the above
Voting is mandatory but moreover is a right of all Australian citizens. Having photo ID, however, is NOT mandatory as we are not (yet) a police state with internal passports and are not required to have our documents with us at all times.
I had an argument with one of the polling officials a few years back when they asked me for my driver's license. I told them I didn't drive (whether or not I do is irrelevant). He then told me I couldn't vote. I asked him if only people who drive were allowed to vote, which confused him for a bit. He then asked if I had a proof of age card and I told him that I didn't drink either. (I so do - far more than my doctor is comfortable with.)
He called over the person with the most impressive lanyard, whom I then continued to argue with off to one side. She confirmed that I needed photo ID and wouldn't budge from that position. I asked her what would happen if I didn't vote and she said I would get a fine. I pointed out that I was in effect being fined for not having a photo ID and that that was rather odd seeing as there is no legal requirement to have a photo ID.
I told her that I had never needed photo ID to vote before and she said that that those were the rules and that was that. I got a fine and replied with the explanation that my polling official had prevented me voting. Never heard a thing back.
Not that it mattered as my seat is about as safe as a set can be.
Now the real TL;DR....
It is fundamentally un-constitutional to require people to have a photographic ID in order to vote. While the question of whether the constitution does in fact guarantee the right to vote was up for debate for a long time, it was fairly much settled in the affirmative in late 2007; Australian citizens have a constitutional right to vote.
Section 41 of the Constitution states that no adult with the right to vote for at the state level shall be prevented by any Commonwealth law from voting in federal elections. That of course dates from the colonial period but taken with s7 and s21, and the (relatively) recent judicial interpretation that they do in fact guarantee the right to vote, the Constitution states that no law shall prevent people from voting.
Constitutional rights have legal primacy and cannot be changed or negated by legislation.
Passing legislation that REQUIRES people to show photographic identification has the side effect that anyone without such ID would then be denied their now confirmed constitutional right to vote.
You might say that the requirement to enrol to vote is therefore unconstitutional and that you should be able to vote without enrolling. It's not been tested but you can indeed vote without enrolling, which is called a 'declaration vote'. Exactly how that works I am not sure but whatever.
Sure, having photo ID might be a requirement of setting up a PO Box but then access to a PO box is not, so far as I am aware, a constitutional right.