I get why you pointed to '04, but it really isn't the best example. The four team playoff would have been pretty clear-cut:
#1 USC vs. #4 California
#2 Oklahoma vs. #3 Auburn
You can toss out Utah, Louisville and Boise, as the playoff won't include the mid-majors. They have been given a token spot in one of the big 6 bowls, but they won't be playing for the title.
Cal would have gotten in over Texas as their one loss was by 6 points at #1 USC, while Texas got shut out by #2 Oklahoma at a neutral site.
2007 would have been a better example. The BCS was convoluted enough as it was. While Ohio State certainly would have gotten in, and likely LSU, how does one decide between the 7 two-loss teams along with the 11-1 Kansas team with a terrible resume? And that's assuming 12-0 Hawaii isn't considered at all.