Seems like a lot of questions were raised on how you will be able to play with the same group consistently and clan practices. Have these guys never heard of:
1) Private matches
2) Parties
Thats what us console guys do. If we just want to play an unranked game with our own clan members we just set up a private match. And to stick with one group, we start up a party and migrate from one match to another, automagically.
As for clan vs clan battle, I haven't read much on the details, I am sure they have setup something like Killzone where you set up a time and the server creates a room for you at that time. If they haven't implemented this, that would be a HUGE miss by IW.