If I were designing a representative democracy from the ground up, I would have only one house with full proportional representation. I’m not compelled by any of the arguments I’ve seen in favour of multiple systems side by side like we currently have, they generally seem to sacrifice democracy in favour of convenience or “stability”

I’m strongly of the opinion that “government” as applied in the Australian political system (ie, cabinet) should not be a single party, but nominees collectively agreed by parliament (assuming ministers are necessary).

Going from where we are now, the lower house needs to change. Multi member electorates would be great. Otherwise, the smallest meaningful step we could take would be transitioning to a Condorcet method of counting lower house votes. That wouldn’t even require us to change the ballots!