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;
I agree that I would like to see Valetini in the squad if he doesn't go to the under 20 RWC.
I can't see Izzy Perese making it given he isn't getting selected for the Reds currently. Cottrell would be close as a 6 option but I don't think Stewart is there yet.
I still think Kepu is our best THP and looks likely still to be for the RWC next year.
If Pete Samu signs he should be selected.
I'm not sure we will have a lot of debutantes this season given how many new players came into the team in the last year or so. I also think the Ireland series isn't for experimenting. They have a very limited preparation and it is vitally important series for Cheika and the Wallabies.