Ability to specify only certain roles available for the override option

I'd like a central administration menu to control which roles are available to those with the ability to override permissions to that node. I have many roles which I use for different purposes, including roles for use by specific modules (such as Membership and LoginToboggan), and I only want to provide users a few of those roles (e.g. anonymous, authenticated, member) as options to provide the overridden access. This in combination with my other request, to show only a subset of the View, Edit and Delete options, would really make this a very useful and flexible module.