Simplified Permissions

Hi all -- I've been dabbling in this for a while, but I'm finally embarking on a serious plugin to help simplify MODX permissions as I work on the MODX vs. WordPress book due out later this year. The idea of the plugin is to establish common use-cases and make them easy to use.... for WordPress users, this means emulating the standard WordPress roles: Admin, Contributor, Author, Editor, Subscriber... but I'm wondering if other people have common use-cases they'd like to see. If anyone has ideas, or if there's an existing plugin that helps accomplish this already, I'd love to hear about it. Thanks!