Dynamic Shadow Switch in 4.6 for Characters on Mobile

Hi, there :

I would like to setup a dynamic shadow switch for characters on mobile devices.
So, is there a way to setup a movable directional light( because only movable directional lights can cast dynamic shadow on mobile devices now ) which isn’t affect the world, but only cast dynamic shadows for movable actors?
I would like to have this feature for performance reasons which means we can disable dynamic shadows in low end devices.