I believe you are very close to the mark BH. Unfortunately with that squad and likely team we are going to get beaten and from there we will decline further as the RWC approaches.
It is the last opportunity Cheika and cohorts have to look at and evaluate new talent at test level. I would especially like to see players like Clarke, Perese, Valetini, Cottrell, F Fainga'a, DPA, Stewart given a chance now to show if they will be options come RWC time. And Pete Samu too if he's interested. We know what some of the incumbents offer and in many cases it will not be good enough for next year.
From your likely starters and bench, I would start Arnold in place of Coleman because of better form and is now an 80 minute player; Allan A in place of Kepu (again better form and a whole lot more development potential) with Tupou on the bench; drop Koriobete and Naivalu from the squad (no form at all in 2018 - retain Naivalu under observation as he might come back as good as ever after his injury is completely healed); drop Kuridrani (completely out of form with no indication he will improve, also has technique flaws); swap DHP and Folau; drop Phipps altogether as others have better skills and more upside (Powell, maybe Louwrens).
From the squad, I'd drop Simmons altogether (his day has long gone).
If we go with the players you have nominated, and I expect Cheika to pick, then we are surrendering any chance we might have of performing as one of the better teams at the RWC. Bring in some of the promising players from outside the stale squad we've been saddled with the past year or two and we just might unearth a few diamonds who will lead us to a more satisfying result. Miss the opportunity now, and it will be gone until we at last divest ourselves of the current coaching setup.