The most likely future of the Geelong line and issues with upgrading it
Electrifying the Geelong is a hard task itself, but with the recent opening of RRL it makes Geelong Commute like the Pakenham line. It is nearly close to a metropolitan service as it gets as the west has less electrified lines. The problem here is Geelong Commuters want their old regional service back and say RRL was a mistake. But the future is upon us to turn the Regional line, into a Metro line as shown in the PTV plan.
Not such a popular decision but slight changes will be made to make the Geelong line without the spending of billions of dollars into Quadding, but instead turned into a metro line as busy as Pakenham with more stops and longer rail commute. This is what is going to happen but the plus side is that the line will get the major upgrades first like the high capacity signalling and new rolling stock. Your tracks will be upgraded and station will get an upgrade along the whole corridor. I call it the Geelong rail upgrade which is similar to what is happening for the Pakenham line. This is the future you will face, unfortunately. There are not enough funding to provide rail quadruplication here, it will be spent on the Dandenong to Pakenham rail quadruplication.
The all quadruplication approach is just not viable at the moment since the RRL would need full electrification and major changes to plan. It is quite hard to design. A solution where it meets the demands and reduce the costs involved. But can do you do when it is planned by people who draw lines on a map where they have no clue how it could run into the future. I'm sorry this is a let down but in reality this is what is likely to happen and will be a problem for future generations to handle.

Potential plan could look like on the Geelong Line:*
If you want to discuss the whole plan on upgrading the Geelong line is in this thread
https://www.railpage.com.au/f-t11386467.htm
*Just to clarify this thread is seperate from "Geelong electrification and High speed rail". You may continue to discuss here about the bad planning and how the Geelong line will probably become a metro line. Cheers, James