How about getting it cut shoulder length with some long layers and some bit of cutting with texture scissors? Texturing can thin the hair just a little, but you will be suprised how light it will feel. Maybe some highlight/lowlights? I find that best to cover grey. I am looking now to try and find you a picture of what I am talking about with the cut and color.
Maybe something like this in way of cut?
The 1st one?