The lastest version of Class::Trait on my hard drive has experimental support for adding traits at runtime. However, I won't be uploading it right away. So far it works, but I need many more tests to ensure that everything behaves the way it should. There are odd corner cases that most people will never hit but I still need to make sure they work. I've worked on them for hours today and it's time to stop.
If Stevan hadn't made Class::Trait so feature complete, this would have been much easier, but much less useful, too