if you’re smart enough to use patches, you’re smart enough to wrangle SVN. SVN can give you arbitrary diffs between any release or revision of WordPress, compare it to your local version, allow one-click reversions and updates

Yeah, but that wouldn't tell us which changes were for security and which were just bug fixes ... or at least I think that is the case. I don't have a lot of experience with SVN so maybe there is some functionality in there I'm not aware of which tells you what the diff's are for. If so, then it maybe someone will take those and create a site offering information on how to apply them manually perhaps. That's not something I think the WordPress.org project needs to deal with though as it isn't something you should be encouraging people to do since most will be doing it for the wrong reasons.