I found this
https://www.airotronics.com/site/product-delaymake_TGCXB-E.php which could prove very useful, I think.
But you would need a something to reset it every 24 hours. You could probably use one of those programmable timers where you can set a daily times on for 15 minutes.
Your bigger problem is knowing when ON/OFF peak is. If it's strickly time based, then, again, a 7 day timer would work.
I took a brief peek at Australia's energy measuring stuff and dit appears it uses like a 15 or 20 minute interval where data is sent ot the utility from the "smart meter".
It would be cool if you knew when it occurs. I suspect, if I HAD to do the same and the peak times were fixed + and additional announced times,I might consider some sort of automation system where you could email/TXT the time/date of the energy savings period. There were some systems described in Circuit cellar that did just that. They retreived email messages and examined the headers and based HVAC control on that info. Some sytems that you can buy do the same with "password" authentication too. i.e. the password has to be sent in plain text in the message. Usually the purchased systems have a service/server that you subscribe to. I don't think they could get as fancy as you need.
Here (In the US and my state), if I allow the utility to shut off my AC at their whim, I get a reduced rate. If I had electric hot water, they could be allowed to control that too. They install a gizmo that uses the same network as the smart meter that interrupts the compressor signal to the compressor. If you have such devices in Austrailia, try to convince the Utility to provide that info as a dry contact. Maybe, it's even worth a suggestion.
These things are supposedly addressable, so therefore your unit might be able to be programmed to respond to Peak/Off peak rather than the more complex algorithm that they use. They don't have to turn everyone off.
In Canada, fossil fuel is expensive, but electric is cheap. Thus, dual fuel furnaces are useful when you have some sort of demand billing.
I'll think "out of the box" every time.