Whilst new land needs to be developed in the west and services provided to those areas, it's also pragmatic for governments to develop existing pockets of land in the "middle suburbs" a reasonable distance away from the city. Suburbs like Doncaster, Knox, and Rowville.
Previous government estimates have priced a train line to Doncaster at $1billion. Pocket change if you ask me, but to make the development of these lines more financially attactive, the stations themselves need to follow the new metro trains paradigm of commericalization. Train stations can no longer be simply entry points to the public transportation system. They need a mix of community services, office space and retail.
Secondly and importantly new train lines should not create extra bottlenecks inside the city loop. New lines should push forward goals of decentralization. The Doncaster line for example should extend to Ringwood (a transport hub in the Melbourne 2030 plan).
Concepts like transfer hubs also need to be promoted. People should no longer expect a one way ride into the city. Stations outside of the loop, such as Richmond (which by the way needs a major revamp) should act as transport transfer hubs. The Doncaster line feeding through Doncaster - Richmond - Ringwood - Doncaster - creating an outer loop and completely bypassing Flinders St and the City Loop.
These are imporatant pragmatic steps forward in making the Doncaster line a reality. No longer should the Doncaster line be consider an "If" but a "when".