What exactly do you propose?
A tunnel under Glen Huntly Rd? Impossible due to the canal.
Or maybe skyrail down New St then hooking right into Ormond Rd with an elevated terminus above the Elwood shops? I mean the locals would probably try and lynch you for destroying the beauty of their area, but who knows, you may just get away with it.
Perhaps a surface level line through the middle of Elsternwick golf course. I'm sure the 8th green could make way for a nice park n ride. Remember, Elsternwick is a public course, so it wouldn't cost the government anything to turn it into a railway line. Of course, other parts of the line would still need to go through houses, so they would need acquisition, but its alright, the property values aren't through the stratosphere in that part of town, so it wouldn't cost much.
In fact, I really like the idea of a surface level line, especially with a level crossing across the Nepean Highway, that would be ace.
So after that side has been sorted, and your line has been built, then how do you propose to run this line? As a shuttle from Elsternwick station? Or would you send every second Sandy train to Elwood instead. Sorry residents of Brighton, Hampton and Sandringham, you can loose every 2nd train so Elwood can have a station.
Electrified extensions to Wyndham Vale, Melton, Wallan and Clyde are all in the realms of reality. Your idea isn't.