I posted this a while ago on athlon. but in my opinion, it depends.
If all conferences were 10 teams, then they could play a round robin and we can develop an 8 team play off (which has the same number of games as a conference champ game + a 4 team playoff). So a conference champ game would not be necessary, but the requirement to be in the 8 team playoff would be required to win the conference.
If conferences continue to expand, and they want to include all of the teams (which is more likely than reducing the conferences to 10), then the conferences need to expand to 20 teams, 10 in each division, and you would have the winner of the 4 super-conferences to create a 4 team playoff.
Its possible, but that is my answer to solve a problem if a problem were to actually want to be solved.