You're going to hear from constitutional experts later, so I'll, in part, defer to them, but we do have evidence about the answer to that question, and that's the Senate reference case.
It said that section 44 of the Constitution, which allowed Parliament to make exclusive laws about the Senate and the House of Commons, was not sufficient to make a change, because it altered two things: it affected the fundamental nature and role of the Senate and it affected the constitutional architecture.
To answer your question, we need to know about whatever hypothetical voting system would change those two things.