As already mentioned, there are many different figures that have breast size morphs.

The challenge with your request will be finding hair that is floor length.  Conforming hair, or prop hair made with geometry, won't fit the bill for two reasons. One, you'd probably more than likely need to create a morph that makes the hair that long, which will distort the textures. Secondly, lengthening the hair will not make it work as designed because the longer polygons will be stretched out beyond what they were designed to do.

Your only option will be to use dynamic strand-based hair, and I'm not sure that there is one already that is floor length for ANY character. So you're more than likely looking at creating or purchasing a custom-made hair. I might be wrong.