If OK beats OK State, OK should play for the NC. Oregon and Bama had there chance against the coonass hooligans. As much as I dislike LSU, they should not have to beat a team twice.
But what if OSU beats OU?
I would say the highest ranked conference champion that LSU has not already beat.
Everyone who claims to want a playoff should be opposed to a Do-Over in the BCS, and adamantly opposed to in-conference Do-Overs. The BCS should not be double elimination nor a series. And winning your conference should matter. An in-conference BCS Championship game would be like an all AFC Superbowl or a World Series with just National League teams.
If LSU played Bama in New Orleans, and Bama won by 3 points, how can Bama argue it is a better team than LSU? LSU might still land higher in all the computer power ratings because it will have played one more game.
Second, it turns the BCS National Championship game into a regional game. It becomes the CBS SEC Game of the Week.
One can make a better case about Oregon, because Oregon and LSU played at the start of the season, Oregon will have played an extra game (PAC 12 Championship Game), and a LSU-Oregon game matches the SEC Champion against the PAC 10 Champion. But it is still a Do-Over.
If Clemson and VT win out, the winner of the ACC Championship Game has solid claim to play in the BCS Championship.