Be careful doing an Instrument Rating and counting the hours towards your CPL. This will usually only work if you are doing the 200 hour CPL. If you are doing the integrated 150 hour CPL the hours could only be counted if this is a programmed part of the schools 150 hour syllabus which is very rare. Admittedly the 200 hour CPL offers a little more flexibility, but the 150 hour CPL with an Instrument Rating at the end will equate to the same hours with the Instrument rating embedded in the 200 hour CPL.
The taxation office has also ruled that the 200 hour CPL must have GST applied, so i believe this path would be the more expensive option.
In my opinion more prudent to do a GST exempt 150 hour CPL with a night rating included. This will give you the opportunity to work towards the nav requirement, the night requirement, and a working knowledge of the ADF and VOR prior to embarking on the mecir.