The new regional rolling stock will mean that we will have an excess of Xplorers and Endeavours which could be used to provide extra 4 car services to and from Canberra. The track from Goulburn to Canberra really needs to be upgraded to allow 130+ operation.
Gouburn to Bundendore isn't too bad, its the corridor south to Canberra. But agree it wouldn't take much to simply upgrade the track to higher speed without higher cost realignment, although this is desperately needed as well. Any new alignment and major track work on the CBR branch should be focused on achieving 160 km/h.
The line needs Electric trains, no argument from me there, but the electrons are not to be delivered by costly overhead even if the frequency tripled, rather via mobile gen set placed under the floor.
With new trains, service frequency should automatically be increased to 5 trains per day as a starter, roughly
5 am, 7-8 am, midday, 3-4 pm and 5-6 pm, basically trains passing just north of Goulburn most of the time to avoid passing on the single track and adding to delays/reliability issues. That probably works out as 4 sets in rotation, two spending every 2nd night in Canberra.
With some track upgrades, new trains and realignment, Canberra would certainly support an hourly service of a reasonable sized train, but the 3.5h travel time needs to be broken, which isn't that hard.