If they did this tournament you would have to include the belt holders, so that way the winner would be the unified champ. You would need to expand it to at least 8 (4 belt holders, + 4 top contenders). No matter who you include there will be cries of not including somebody.

I would like for them to take the 4 belt holders have them fight their #1 contender then the winner moves on. The likely hood of any of this happening is about as good as me becoming heavy weight champ.