Hi all,
We've spoken a bit about allowing local groups to be changeable by stewards as global groups are. Well, after an hour or so's work, I have in my working copy changes to the MediaWiki core which will allow local groups to be changeable just as global groups are, on a new special page (I've been able to co-opt the Special:GlobalGroupPermissions interface for Special:GroupRights, which is the new interface for changing these rights. The CentralAuth version is now a subclass of this page.)
The rough working of it is a new source of user rights - group_rights table. This is heavily cached (in-process, on the filesystem, in memcached), and will be loaded any time somebody would have otherwise requested $wgGroupPermissions. $wgGroupPermissions is strictly for configuration now - all places using it have been converted to use a static method of the User object called getAllGroupPermissions.
I've still got to import messages, look into making addgroups/removegroups changeable on-wiki, and a few other things, but, within a few days, I should be ready to check this in, provided the schema change is okay with Brion, Tim, et cetera.
Thanks