My optimistic assumption is that one day, there will be an express train from Bairnsdale to Flinders St, that only stops at 2 stations, obviously skipping Stratford.Nothing wrong with optimism. A future express from Bairnsdale sounds good in theory, assuming everyone who gets on the train at Bairnsdale actually wants to go to one of the two stations that the train stops at. And until there's a more intensive service on the Bairnsdale line east of Traralgon, I'm pretty sure all Bairnsdale trains will be continuing to stop at Stratford, Sale and Rosedale.
Your estimate of what needs to be demolished is wrong. Also, there is no need to close the existing station. It is easier to keep the existing station and train line.A bit hard to keep the existing station if the track is realigned away from it.
My estimate wasn't wrong. It was just based on a different alignment to your 1600m one.

I drew a 1600m radius curve using freemaptools.com. The 1600m curve actually crosses just above the intersection of McFarlane St and Dixon St. Then it goes through middle of Market Reserve. Rejoins existing line at approx 15 Industrial Ave.As I mentioned, there are also new houses (to the north of Market Reserve) which do not appear on Google Earth.
On Google Earth, it looks like 4 industrial buildings have to be demolised. I will guess 4 industrial buildings cost no more than $3 million. (Plus some existing properties will have partial land resumption.) At the same time as easing the curve, the Princes Hwy will have to be rebuilt as 2 bridges over the existing line plus new line. The cost of building the road will dwarf the property acquisition cost.
The google images are out of date and streetview is far worse. I live 100m away from the site, so I see the realignment as being far more difficult than drawing a line on a map.

So, based on assumption that there is an express train, it is worth while to build the eased line, and at the same time, remove the highway railway crossing.And as there is no express train, and there is unlikely to be one for many years - if at all, then it's not worth it.
Sure, if some future government decides to throw the money into a major upgrade of the line with far more frequent services - which would require long passing loops / partial or full duplication, then I'm sure they will also have the money to realign that curve north of the (recently renewed and extended) station platform.