You're ambitious, Myrtone
, but overlooking how risk averse we are with design here.
I do personally feel that Double Deckers could work on a few certain lines, myself. Sunbury
, future Melton
, and Werribee
, coming to mind specifically. And all have the main advantage of largely having quite spaced apart stations and relatively easy routes to prepare for the additional loading gauge required.
But there's problems that work against this concept. We don't want another split like the currently ongoing Siemens on one half
, X'traps on the other
issue that's currently going on, and there's an inherent risk that if the proposed new Double Decker sets turn out to have a problem inherent to the Double Decker design itself (such as the mentioned lack of doors, even if they were very very wide like in Sydney, causing incredibly overblown dwell times at key stations), that, to such an extent, makes the sets an operational liability, we would essentially have to scrap or sell the sets (likely to Sydney), and lose a lot of money on both the investment on getting the infrastructure ready, and for the design of the new sets themselves.
Again, I do personally think there's a potential future for Double Decker EMUs in Melbourne, but there is a lot working against them. And we're just extremely risk averse peoples as a whole, in this country.
Just remember, with situations like this, the phrase to remember is "If it aint broke, don't fix it".