So if Foley goes down - KB (Kurtley Beale) moves to 10 and Hodge to 12? How long since KB (Kurtley Beale) has played 10 at test level? Why do we make 3 changes - possibly on the run? I think every other tier 1 nation carries a spare 10 who has been playing there because 3 changes to a backlit in a test probably is not the way to go. Still Foley is incredibly durable.
Hunt might be the guy to come into 12 now. Meakes is another option at 12 with Hodge remaining on the wing.
If you think your second best 10 is a guy somewhere else in the XV then it makes sense not to carry a backup 10 on the bench.
If Cooper is a couple of injuries outside the matchday 23 then it is reasonable for him not to be in a quad of 32 or thereabouts.
You can disagree with what Cheika thinks the pecking order of his 10s are but once he's come to the conclusion that Cooper is 4th in line, there's not a lot of point having him in the squad.