You do realise this is a 4 year old thread? Don't you?
You do also realise that this concept was killed off under the Baillieu Government 6 years ago after they ran a study to investigate the viability of such a service? Don't you?
And I expect that you are also aware of the pending gauge conversion of the Geelong to Ballarat railway?
Equally, I expect you are aware of the appalling condition of both the Maryborough to Castlemaine line and the Inglewood to Eaglehawk line meaning there is zero chance any passenger train can run between Maryborough and Bendigo without a complete line rebuild, similar to what we have just seen with the Ararat to Maryborough line. This would be hideously expensive. Which is fine if it is on a line that generates a decent amount of traffic, the reason these lines have deteriorated as badly as they have though is that there is no traffic, therefore there is nobody to pay for the upgrade.
Maryborough to Bendigo isn't going to happen, not for the next 20 years at the very least.
On the other hand, do I think there is some merit of running 3 or 4 trains per day from Maryborough to Geelong via Ballarat on the Standard Gauge. Although that would require a new standard gauge line from North Geelong C to Geelong station, and it would also require sufficient standard gauge rollingstock, neither are things V/Line currently have at their disposal. So it won't come cheap.
As for today's little Vlocity via Meredith adventures, they are nothing new. Vlocities have been running out of service on this line for a few years now, usually when the main Ballarat line is closed (like it is this week), it means nothing.