Single Clan champaign can be a lot of fun, they allow the players to directly face problems that the Clan faces. Taking a story that might be a side plot for a single character into a full blown campaign.
Most Clans have their own flavour of all type of jobs, however some players might feel limited by not having builds from other clans available. An easy way to deal with this is to have characters have married into the Clan.
Allow players to take this for free should they have another player to play their spouse. This will keep your game from being over run by people who are not really part of the clan you want to run. I also suggest limitting the number of characters like this to a maximum of two.
If the players you wish to allow to play these in Clan not in Clan types, please feel free to get them to take Disadvantages such as, Bitter Betrothal, True Love, Obligation. Or get the player to take the different Schools Advantage.
A result of a game like this is that you can allow the characters to be more open with one another. Scorpions can plan how to infiltrate, or perform long Cons. Lion can have their own regiment. Crab can go about as a group of Witch Hunters.
There are a lot of good Storytelling possibilities when you take a Clan's focus and make it the focus of the campaign it can be a lot of fun.