Let's look at this on its face. A major reason the Aus top four has sucked so convincingly is because nobody is there to breathe down their neck. I'd go so far to say that the golden years happened not only because of the talent and dedication of the first XI's batting, but the knowledge that they were perfectly replaceable meant they were willing to scrap for every run.
Right now, everyone batting above Clarke has copped a torrent of criticism since the South Africa tests and any changes made have been strictly short-term (i.e. Hughes being babysat till Sri Lanka, Watto's recovery from his last broken nail).
You can't help but feel that the top four is certain their spots are secure irrespective of performance, simply because they're the best we've got and Invers will persist in patiently waving aside every failure until they develop proper Test temperaments in their own centrally-contracted time.
So, for the Ashes, why not have two players - one a Test veteran, the other spending half their life pounding attacks on English decks - waiting in the wings or even used as outright bolter selections David-Steele style?
In any case, they'd be an urgent injection of maturity into the squad proper, even if they don't play a Test.