Okay, a few thoughts from me. I think that it should be done in three stages. Firstly, the tougher one, Rushall to Southern Cross, with terminating facilities provided underground at Southern Cross. Stations would be at Clifton Hill, Fitzroy, Parkville (perhaps closer to Lygon street, with seamless interchange with Metro 1 services) and Flagstaff (closer to the QVM, with seamless interchange with MURL services).Stage two would have a new set of underground platforms built at Southern Cross (perhaps done during stage one to save costs) for Geelong/Warrnambool services. The existing underground terminus at Southern Cross would continue and run parallel to Geelong services, both in separate, two tracked tunnels, with a station at Fishermans Bend for Werribee trains and then at Newport for both Geelong and Werribee trains. Just beyond the existing Altona Junction, these four tracks would come to ground, running alongside each other to Werribee.Stage three would involve the opening of extensions enabled by the new tunnel/s. The long awaited Doncaster extension should run via Clifton Hill for interchange if possible. The Altona loop would be no longer, instead running beyond Westona to Point Cook. RRL would be electrified with services to West Werribee Junction to interchange with Geelong services. That's all I can think of for now.