I think the 3 x Q400's talk was all before QLink knew about the WA runs. All they have now is Exmouth and Geraldton.
It'll be a fair amount of time and money to do a setup for just 3 aircraft over 1/2 runs. Having said that, anything is possible. But with Network already setup over there, they'll be the obvious vehicle of choice.
ADL only works because of its proximity to the East Coast.