I think Granita in the line would be great. The Rock People always seemed kinda lacking with just two at the helm - Rokkon and Stonedar (as much as I like them).
I would also love to see the other Rock People down the line as well. Granita is a necessary first step to expand them as a force. Now, this is coming from a Rock Lords fan, so I'm a bit bias when it comes to rock toys.
As for parts, Granita will probably need her own. Of course, once you make Granita, you've got a mold to make other lady Rock People.