Can your question be rephrased as "Which is easier - to move HP or to move Perth?".
Looking in the table REP_TIME_ZONE (in ver. 4.5), there is no apparent column that indicates whether or not the time zone has daylight savings time. So even if it were legal, I am not sure how adding a row to this table would help.
If worse comes to worse, you might think of manually changing the offset for AWST when you switch from summer to winter time (but this, too, is unsupported tinkering in the database).
Try getting HP to move on this. I am sure you will find a lot of mates here ready to vote for this request.
In the meantime you can change the time zone for all Perth users (ie in their Account records) to Japan Standard Time (UTC+9) which will work for everything entered since the change to Daylight Savings in WA. Then change it back at the end. Of course if the user displays a record with any date/time before the change, it will be an hour out. If your Mgt Server is in Perth then you'll need to change it's time zone too and restart else times in logs will be wrong.