"Heritage Listing" is a disaster because it has gone too far.
This applies in general, not just to railway infrastructure.
In general, when you have 10 examples of an architectural design heritage listed, that is enough.
As an example, if there is a street / area with houses built in the 1890, preserve 10 of the houses and let the rest be demolished for new development.
I agree the Flinders St Station BUILDING should be preserved and incorporated into any new design.
That is because it is iconic, and obviously there aren't 10 of them.
However, a heritage listing of the platforms is pathetic, stupid and a total waste of time.
What should simply happen is a video record of the current platforms is made. And photos. Plus any architectural drawings.
It is not hard to make a video, gunzels would do it for free. It can be put on youtube.
This provides a documented history of the building.
There should be enough information, that it is theoretically possible to rebuild the station with today's design.
When that criteria has been met, there is no need to physically preserve the platforms, and they can be destroyed and rebuilt to a more modern design.