Unaware is a brilliant ability for this CAP, maybe too much so, as repeated plays against Quagsire have taught me. Set up sweepers have their momentum stopped in their tracks, helped by its natural bulkiness (much more so than Quagsire). However, it only stops an ASPECT of the opponent's momentum, and as such is only truly useful against set-up sweepers.
I feel that Contrary has a lot of potential dependant on the CAP's movepool, but it would be treading an awfully fine line, as we've seen with Serperior's immense Leaf Storms climbing it straight to DW OU. Reversing Intimidates, etcetera. Given the CAP's below-par attack stat, a Close Combat would serve to add straight to its bulk while chipping away at the opponent's health, slowly turning it into an immense wall, whereas Superpower would increase its sub-par attack and add to its great defense. However, as I said before, this would need to be covered VERY carefully, as it is borderline overpowered.
Trace is a great one in general, allowing for the CAP to catch up with the various weather abuse teams (assuming it traces a swift swim/chlorophyll/sand rush pokemon), and is also useful in general for scouting opponent's abilities to get a grasp of what that pokemon's momentum gaining plan is and using it to your advantage.
Magic Mirror is a great ability, but it may not be able to see much use considering the lack of entry hazards in the 5th gen metagame... was what I thought before I forgot it bounced back status moves too. Could be very, very good.