A good start would be double track SG from Craigieburn to Tottenham, without stuffing up the Metro. It is a huge ask.
When ARTC and Inland Rail finally get their act together in 20+ years, then we can resume this discussion for Shepparton/Toc/Deni.
In the meantime there is nothing stopping NSWGR building tracks north bound from Deni, except of course a favourable business case.
I think that first part is a good idea as well. If you can get 2 tracks all the way from albion to seymour for SG and keep the existing 2 BG tracks that would be nice.
I agree but if where still talking about this in 20+ years then will become 40 or 60 years.
Getting the line converted to SG would help make that business case more favourable.