Is there a way to use models in asset bundles like the Character Customization example together with the Locomotion System example?
I wish to have a customizable avatar whose walk cycle is driven by input from a Wii balance board for example.
Sure. There's any number of ways to use asset bundles and a locomotion system together. They are not mutually exclusive in any way. Asset bundles are as they are named, bundles of assets, and can be used to store and retrieve assets for use in your scene. A locomotion system is merely a variety of scripts which maintain and control information about movement and world interaction. You could easily have the locomotion system driving the motion of assets loaded from asset bundles.
As long as you have the interface by which to retrieve and handle input from the Wii balance board, you could easily do that with a some work and a working knowledge of scripting.