Rock is for WM. It would be good for him to take on Randy. Both were considered the youngest heavyweight champion, and seems like a decent draw. Randy's pretty much about to go on PT schedule too, so it would be kinda cool to show some old clips before he goes out to pasture.
Batista will be doing promotion for Spectre, so RR would be a good time for them to war, with hopefully Evolution standing together with some fukkery in the match (Brock kicks all their asses though). Unless Brock v Rock will be for title, then one of them has to win Rumble. Prefer Brock.
2nd choice would be Cesaro, if he's not in line to revolutionize the IC belt prestige in epic feud with KO.
Brother, I didn't think about it, but him vs Batista could be a money match.