Ok TWAS, I'll see if I can throw some light on the matter.
I believe the backline needs very little tweaking. It is pretty good as is and seems to be developing with more game time, but in reality we could expect at least two changes to be made as Speight and Beale become eligible or fit and healthy. Moggy might also force his way back in as fullback cover.
I do see a need for significant change in the forwards. Some changes will take care of themselves, being Pocock and Higgers imo. Both the front row and the second row need some drastic action. I do think Robbo needs to come into the starting lineup and be given first go at the LH position. I would rather have Sio as backup LH because by RWC time I think he will be indispensible. Slipper's best option in my opinion is at TH but he may not even consistently perform there, so we need to be bringing one or two others through just in case. I see these as being Dan Palmer and Salesi Manu. The current second row pairing is the most under-performing pair I can remember seeing in 20 - 30 years watching. Timani just doesn't cut it at test level. Tried and found wanting on many occasions. Kev is not playing at the required standard either atm. This might be due to injury; time will tell. If Horwill doesn't soon make a full recovery, with the RWC in mind, we will need to be establishing a whole new second row, including reserves.
In summary, I see the need to find two new starting props and two new starting second rowers. On top of that we should be looking for at least two or three reserve props (though Slipper might be one of those), two or three new second rowers, and another couple of back rowers at least to back up Fardy/Pocock/Higgers.
Then we have the likely inclusion of a couple at least new backs.
So who are the going to jettison to bring in maybe 10 - 12 new bodies? Seems like a lot of change in the wind to me.
What I'm getting at though who do we replace them with who isn't already injured or failed?
In the front row Palmer is gone, Manu whilst I noticed and thought looks ok has done nothing to warrant a chance and Sio looked the goods, then arguably did less than Slipper in his multiple games for the Wallabies. We have 2/3 of one of the strongest Super Rugby front rows now. I don't see any of the other blokes who have been scrumming like they are on ice skates all year making a huge difference.
Simmons and Horwill have been one of the stronger second row combinations we have. Carter has shown he is worthy of a chance yes, and Pyle has been noticeable but there is doubt over whether he is up to it and is injured anyway.
In the backrow Pocock, Higgers, Alelua, Palu and whoever else are injured, Hooper and Fardy have been our 2 best performers so I can't see massive improvement there, because the supposed guns we have on the sidelines are likely to replace them, and suffer the same issues of lack of support.
I agree on the backs. Genia has been fucking putrid, but White has been average other than his run on debut. Never thought I'd say it, but maybe Phipps is worth a start?
As for 10-12-13: Cooper, To'omua and Kuridrani seems to be getting better together, I'd love to see more work on the defence of them but there appears to be a good balance there.
Back 3 is maybe a bit up in the air. Izzy has been very good as a player, but perhaps not as good when judged solely as a fullback, AAC (Adam Ashley-Cooper) whilst not the greatest winger in the world, I'd like to see 2 wingers playing the house down to replace him as he does offer a fair bit, and then there is Cummins/Tomane on the other pick and swing who have both shown a bit in their chances.
I guess what I'm getting to is perhaps Sio might be worth another crack, but he looked to be the form Aussie Loosehead and got chewed up a bit, and Carter possibly. At the same time Simmons has been our best lock this international season and Horwill has been our best lock in years and fully fit will be our best. Other than that, nobody is actually knocking on the door so not sure what there is to change.