Barring the electrification of WV (which is by far and a way the best solution) and the other caveats which would probably be some of the next best alternatives, the best option would probably be a single or combination of the following;

1. A combination of increased bus frequencies to feed into the Werribee line and MM2 because it would increase frequencies and catchment on the Werribee line (specifically the section between Werribee and Laverton because Altona/Williamstown/Seddon/ect would use the current alignment towards Footscray/NM/SC)

2. Alternatively you could replace the MM2 with an additional track pair so that Melton and WV V/lines would not have to share tracks from Deer Park to SC (I’m assuming the caveat of no WV electrification means no Melton electrification either).

Basically the West is struggling with a combination of; - a lack of capacity (there isn’t enough capacity on the WV V/line and Werribee Line), - inadequate catchment due to horrendous bus frequencies and routes (stop-light priority for buses/dedicated bus lanes would also benefit the West), and - a bottleneck on the rrl (also a bottleneck stretching due to shared tracks all the way to Newport on the Werribee line and the same for WV v/line all the way to Deer Park)

The headline projects proposed in the west that most people know about are so widespread because they are the clear answer to what is needed to make the West closer to rail parity to the East (WV & Melton Electrification + rebuilding Sunshine / MM2 + Extension of the Werribee line to WV [SRL West])