Gaia is working on better and easier use of shape keys in AvaStar. Watch the teaser:
These are only for use in Blender. They cannot be transferred into Second Life. SL shapes are baked into the viewer, meaning users cannot change them. But, they should allow us to make our various shapes for clothing and transfer the clothing into SL.
For instance, if I understood correctly, the shapes we personally model for, say large, medium, and small, could be setup in shape-keys and we could click between them. That would make a number of things easier.
No release date.