In the late '90s there was talk of moving a fighter squadron up to Tindal in order to ease congestion at Willy. The reason the concept was axed? Katherine did/does not have the infrastructure to support the influx of several hundred people at once. Defence could support the move, however, healthcare and hospitals, housing, education, private enterprise for spousal employment etc dollars don't come from the defence budget (not my words, I'm paraphrasing the CAF of the day).
Notwithstanding our contractual arrangement with the RSAF, I'd imagine there'd be similar issues moving an even larger amount of people to Learmonth.
Does anyone remember the Dubbo superbase concept?