I don't see this as a huge problem, this aligning of the presentation of the budget and the tabling of the estimates. The delay is not as important in my view. What is more important is to provide windows of opportunity for members of Parliament who are on committees to influence the government. Parliament approves spending only in a narrow, formal, and legal way. The actual votes don't change the estimates. If they do, it's very rare.
I don't see the problem of having the budget speech, which is a great big policy document and not so much about the details of spending.... Also, then, the estimates themselves are sort of medium-sized policy statements, and I think they should be the subject of ongoing scrutiny, as opposed to saying that by a certain date in the year all the estimates have to be approved, and if MPs can't fit in meaningful scrutiny during that compressed period of time, then too bad for them.
I'd rather that you take a longer-range view of things and seek to influence government spending in the outer years of a mandate.
I don't know how they get around the problem in Australia. I just don't have enough knowledge of that.