The next Melbourne stadium

[Johnny Bananas]

Fair point on electrifying the longer lines, especially the Sydney and Adelaide links that would require co-operation with other states.
Although, would they need to be electrified the whole way? It still would allow for the build over the station, without the fumes, if they ran on electricity only within Melbourne and diesel outside city area.

That's a good point, but it'd require an entirely new fleet. I did a little reading and found NSW are replacing their entire regional fleet with bi-mode multiple units that can do exactly what you describe. In Victoria however, the issue is that VLocity trains only run on diesel, and they're still being manufactured. Given they have a planned usage of 35 years, it seems like the plan is to keep using pure diesel trains until at least 2060. Perhaps a future government could embark on a project to renovate the existing fleet to become bi-mode multiple units, but I'm not sure if that's even technically feasible.