Right, cleanup stuffs like I started off with would be easy enough to do now. And reasonably common extensions are covered by things like Alexandria. But going to more generics introduces a potential performance hit without the implementations being onboard to improve how they handle generic functions and method dispatch. And then there are other enhancements (like concurrency) that are bounded, with regards to portability, by whatever implementations uniformly make available. So any changes there will require implementations to be involved if it's going to result in portable code. Otherwise you'll have people implementing things using, maybe, CFFI and tying it to a particular implementation, OS, and set of external libraries, which breaks portability.