I will push for us to discuss making a read-only mirror with OSU. However, I think there are complications with hosting and svn respecting mod rewrite rules (if we wanted to host it somewhere else like google code and rewrite the url on access), but I could be wrong about that. So currently I would assume we cannot do it, and move on from there.
I have to agree with Dirk, we should poke the people tied to the packages in your grep output to update their links, and if there are not maintainers to update those links then there isn't much we can do about it. I'll put together a list and email ros-users to remind people.