It is already almost impossible to find 2 award seats in F, getting 4 and then on multiple flights is extremely unlikely. Why don't you get accounts at several of the OW airlines and check availability for award tickets? This will give you a better idea of what is possible.
Airlines often open seats for awards between a two weeks and a few days before the flight. Assuming that your want to plan ahead and not want to be stuck somewhere mid trip because you cannot find seats this does not help.
Splitting up into different classes or onto different flights could also be an option, but depending on where you want to go you most likely will spend a lot of time searching for flights.
Also look at flights via Japan (in combination with JAL, no F to Australia), CX (also no F to Australia) and some other routings with other OW members.

Good luck.