Sounds like a nice idea, Dante. I can appreciate why those of us who sell items that are really and truly fully copy/mod would want this.
It's more difficult the more I think about it though. Eg- boxed items. Clothing creators sell a mixture of perms in one package- ie copy/mod prim attachments with no-mod/copy clothing layers. (One reason why I prefer to shop inworld is so I can click to see the perms on individual items in a box.)
While I'm thinking about this, we really do need an extra permissions category for all those items which are moddable yet contain no-mod scripts.