The main issue with the Short Term Tickets of the touch variety is that they cost 30c a pop to produce.
Given that a single ticket in the Regional cities is only 10c more expensive than the myki equivalent fare, that's not economical. One might argue that the costs are much better stacked in Melbourne, where the price difference would cover the cost of the ticket, and be enough incentive to get a myki over a short term ticket. For a Geelong passenger, 50c a week isn't very much to pay to buy a ticket every day compared with a myki...
I've often wondered how costs per 2hr/daily/etc are decided for a particular area.
The way I'd probably do that would be to define equal geographic areas, not taking into account total population or population spread, but taking into account the average vehicle loading, route frequencies and route operation hours, and use the area with the median score as a base value (as a percentage of total running costs for the entire statewide system), then multiply or divide for all other geographic areas.
However, all prices would be rounded to the nearest $0.50 (half-day or less), $2.00 (daily), $5.00 (weekly), etc. for simplicity. And this formula would be used every time, with the median figure and scoring recalculated from scratch every year rather than simply having a CPI figure added.
Then, the total of revenue plus subsidy (after Metlink/PTDA running costs) to be given to operators would be divided by geographic area based on patronage, and between modes within each of those areas.
I have specified geographic areas rather than population areas because that means there will be a constant number of areas of fairly equal sizes (so no redrawing of boundaries will be necessary until/unless the states are abolished despite the constitution), and changes to ticket prices over time will reflect changes in service rather than changes in local population - which I hope would encourage greater service coverage.
(Note however that I've come up with this at 3am in about ten minutes...)