"Geelong passengers could change to werribee trains at werribee if they need to go to any station before southern cross"
Considering the fuss still being kicked up by some Geelong passengers over the RRL skipping North Melbourne and forcing them to change trains at Footscray, this may be a tough sell for some.
A lot of the arguments here seem to be working from the assumption that the idea is to improve the service from Geelong to Melbourne, when any close look at the reality of transport planning in the region for the last twenty years would suggest that the real idea is to improve the services from areas around Geelong by allowing them access to the Geelong service.
New lines to Torquay and Drysdale will put more people onto the already crowded trains to Melbourne, as will the planned new stations between Wyndham Vale and Deer Park. A tunnel from Newport through Fisherman's Bend to Southern Cross might be built in the medium term, but if so it seems much more likely it'll be used to get more people from Werribee and Point Cook into the city, not to improve the Geelong service.
It seems as though those in charge feel that Geelong-Melbourne currently runs on a perfectly good set of tracks, and any expansions planned will be designed to allow more people access to those tracks.
Geelong passengers hated the fact that their train went right past North Melbourne station and did not stop, when it did so previously. Geelong trains have traditionally stopped at Werribee, Newport, Footscray and North Melbourne. Returning the Geelong line to this corridor, and having some passengers change at Werribee would just be a continuation of old habits pre-RRL.
I agree new lines to Torquay and Drysdale should also be on the cards, but if the government is keen on decentralisation, then it needs an effective and quick way for Geelong commuters to reach the city. With the vaccant land between Torquay and Geelong quickly filling, it's only a matter of time where the demand for trains between Geelong and Melbourne require a dedicated track path into the city.
With talks of Metro Tunnel 2, linking Werribee to Mernda, it would make sense to kill two birds with one stone and combine this project with a dedicated track pair to geelong (both projects are definitely 20 to 30 years down the track, so this need is not unforseen). But as we know (like CD9), the government is not always smart with how it can save money by combining projects (Dandenong Quadding at same time as level crossing removals).
Geelong passengers can access North Melbourne via Footscray, not just a big deal, since they're are many trains for connection and only add a few minutes to the journey. For the rest, adding Werribee line to Wyndham Vale for interchange will solve most of these problems.
To fix the problems of the growing patronage of the two Metropolitan stop and future stop as shown in maps is to make the Werribee line extended onto current RRL tracks and put two new tracks that will express through and another two track will do the same between DeerPark to Sunshine. Then Geelong service would run like this Little River-Wyndham Vale-DeerPark-Sunshine-Footscray-Southerncross. That doesn't sound to bad getting into the city and as five interchanges in Melbourne to choose from.
It kills two stones by Quadding Sunshine and Deerpark, then Quad between Tarneit and Wyndham Vale. So Ballarat trains can be separated from the Melton line.
And another is that if you want to fully seperate the Geelong line, I don't see how you gonna provide two extra track from Yarraville-Southern Cross. It would need to still connect with existing RRL. Even the Ballarat and Geelong lines are fine on the track, even at the max frequency 20 minutes they still run 10 minute, if you add Bendigo to the mix it be 6.5 minutes. If the Geelong line got to frequencies of 10 minutes then I would consider the two extra track between Sunshine and Southern Cross, when it is electrified.
The project I set achieves basically the same objective with your plan but will be 10 times cheaper and less disruptive than your plan. RRL is not in built up area, Werribee line is. Makes a hell of a difference in construction. Plus the acquisitions on Yarraville. Yeah tell that to the residents they will be pleased.
I don't see any issues with my plan other than the North Melbourne issue.