It feels like we were getting some momentum here on an important but long-dormant issue here... maybe it's time to move this discussion to rack-devel? Perhaps there's another Rack luminary who can lead the charge, or at least see if there's some consensus after a few more years of shared experience on what "sane" encodings might look like.
A lightweight way to move the implementation forward might be a simple Rack middleware gem which sets the new encodings on the environment, or adding the functionality to rack itself. Once developers were comfortable with the new regime, the app servers could follow suit and put those encodings in the env natively, and the Rubyland implementation of the new encodings could be dropped. Gary
