Generally, my bottom line is that I want cc to only include already-established leagues, since I don't want status on cc to confer a degree of legitimacy to your league to help with your clan recruitment. More practically, this means that I want your league to have existed publicly for about half a year and, throughout that time, have had an amount of clans such that you can achieve a good sync success rate consistently amongst only yourselves.
The other two ways to enter are to be created from the branching-off from an existing league, which I don't think you are, and to get the approval of all the leagues on the system to add you, since if nobody cares about it I won't care either.