Mirror shape-key

Blender's mirroring approach is stunning, there no parallel. But I would like to have mirror also for shape-keys. Every time I have to build two shape-keys which are symmetrical I have to "new shape from mix", re-name and "mirror". This is boring and time consuming. The ideal is that shape-keys code would acknowledge two shape-keys which are symmetrical by the naming of them ("_R,", "_L"), just like bones system do.