There is definitely merit in this idea! 

In response to your query there is no specified length of time that you have to live in the property in order to make a place your main residence exemption, the main thing you have to keep in mind though is that you have to keep on renting.  As soon as you purchase another property that you choose to live in your situation changes.

I am in the same boat at the moment, however in Melbourne.  Finding something within our price range in an inner city/bayside suburb that hasn't taken off is proving to be a struggle!