Ah, yes. The GG. A remnant of colonialism. Did you know Australian governments at first did not even have a say in who it's going to be? Was a British guy for a while.
Anyway, your statement said it all. You want us to have a foreign-born HoS - you even call it "a great part" of what Australia is. I'm not going to convince you, then. You haven't really made one compelling argument for the Monarchy, just stating a few times that you like it and would like it to stay. The rest was an appeal to the majority.
You try to minimise the cultural impact of the Monarchy when it suits you (e.g. by saying that the implications of being a Monarchy are irrelevant), and then do go on to state how great it is. Please choose which one it is.
Canada has its own flag, at least, rather than having the Union Jack and a tiny Southern Cross on it. It's also a bit of a special case, since most people (erroneously) believe that it got rid of the Queen. Shows at least that they do their PR better than us.

You do correctly state that we haven't made as much of an effort to distance ourselves from this archaic institution.
You're constantly appealing to the will of the majority, which is a very weak form of argument. Public opinion changes very often, and the fact the majority wants something should not be used to stifle dissent. I'll also make a note of the fact that we actually opposed the Monarchy for most of the past 25 years, and also that the vast majority of Federal Parliamentarians are republicans. Howard specifically wrote the text of the 1999 referendum so that it would fail, thereby bringing the republican movement back decades.
That last argument is probably the silliest one in existence. Most of Europe (Germany, Austria, Italy, Ireland, Israel...) have managed to come up with a way to pick tier President. You could simply take the Queen out of the picture, and just had the government appointing the President in the same way a GG is, removing her out of the picture. Or you could had direct elections, a la Ireland. Or have secret Parliamentary ballots, like most parliamentary democracies in the world.