can not speak for AUS rules Flying
In JAA Land:
In general you can not act as a crew member for hire and reward without a professional licence, and if the aircraft requires a TR, then a valid type rating. A current medical of the class required, plus if flying IFR an IR.
But, always but, you do not need the professional licence if flying, on an aircraft owned by a company which employes you in another capacity, and not as a pilot, and all the other boxes are ticked.
But, the tax authorities, MIGHT ask to tax you on the benefit in kind that you receive, for free P1 time.
Never easy,
I part agree with CHOCKS, but in practice would say his route is not practical.
So my opinion is yes you are legal, wrt to the other points above, but do not ask for any consideration for your excess skills.
glf