Does it have to be two Clans? Or is the term "clan" being used outside of BT parlance/canon to denote two "teams".
If, in the latter case, "clans" is being used to describe two teams (which I believe was common in the ladder leagues), then it is obvious we no longer need the IS, since everybody wants to be "Clan" anyway and we can just have MWLL played in Clan space.
And don't give me any crap about semantics, the distinction of Clan and team is very precise when playing a MW themed game, particularly with respect to a planetary league.
Clan and IS house (with its minions - mercs and pirates) = BT/MW, team = any game.
Get with the program now to avoid confusion in the future. If we are playing MW:LL with the view towards a planetary league, think MW with Clans, IS houses, Mercs and Pirates. A MW-based planetary league depends on strict adherence to vernacular, a ladder league does not operate as strictly (if using "clan" to describe ANY team). Even if you are thinking towards a simple ladder league, I still think a distinction should be made in the MW:LL forums since there will likely be both camps of thought.