Captaincy I think has really been a boon for Australia this year.
Slipper was a stalwart during his time at the Reds and I don't think anyone would begrudge him the Wallabies job but as always it's tough to name a prop who is very risky due to scrum cards, and they'll probably only play 60 odd min. AAAA has been awesome for the Brumbies but probably can't be considered because Tupou is just too good. I feel like To'omua (or perhaps it's just the Rebels/Wessels) has been very binary in either going for the 3 or going for tries. To contrast that O'Connor has been steering the Reds around nearly flawlessly finding a way to keep his team in the fight when they are on the ropes, but also pushing his lads when they need to be pushed, and calling out his team/players out when they need it, and taking pressure off when they need it by taking it on himself.
I think O'Connor almost has to be at least considered for the Wallabies Captaincy the work he is doing with the Reds... His media interviews etc have been as good as anyone. Also him not being the 'normal' captain for the Reds probably counts for him in that one, so he can really focus in on the Wallabies. I think right now O'Connor has been as good as anyone ever has been for any team in Australia -- perhaps anywhere ever. Personally, I'd have him as the Wallabies Captain right now.