I'd suggest this is more a long term issue that the ARU has been no doubt thinking about for some time. Cheika would have certainly had some imput, but it doesn't necessarily mean that this was all about him wanting to select a particular player from overseas. I'd suggest the biggest factor in this decision being made now is what is about to happen in 2016. 2016 will be the worst year yet for the wallabies in terms of losing experience. AAC (Adam Ashley-Cooper), Kepu, Cooper, Genia, Palu, White, etc all leaving. Cheika's main goal is surely to bring home a Bledisloe over the next 2 or 3 years and his chances of doing that with so much experience leaving are low. In particular Kepu is a major loss, because we haven't yet developed quality THPs to replace him. I think this is a preemptive strike more than anything.
If Cheika was planning on selecting a player overseas I'd say it was Douglas and that he'd discussed with the ARU a rule about allowing him to play provided he contracted with ARU to return home. We'll never know now that he's injured.