I see no reason to not allow more than clans if they want to participate. Round robin qualification schemes used in JJ2WC work just as well with numbers that are not powers of 2 (ie 9,10,...) and numbers that are greater than 10 as it seems you want now.
For example, if we had 12 teams 3 groups of 4 would work well and you can have successive round robin style play. (But this is only one possibility, there are many other valid schemes to consider.)

Now, on the first post there was also no mention of a maximum number of clans, only a two week deadline to register. It should have been mentioned that there would only be 10 clans paricipating and that you need to register as fast as possible to guarantee yourself a spot.