Read TypeRep? standard for typeRepKey?

is there a reason why there is a Show TypeRep, but no Read TypeRep? and isn't it time to standardise typeRepKeys? something based on package name/version, module, name, so that one could rely on being able to read in what one writes out, and on TypeRep-based maps being compatible accross programs (at least as long as the versions match)? i was thinking about improving the reading of existentially typed data (see haskell-cafe thread) of that name, and was surprised to find that Data.Typeable doesn't quite support these things. or is there a workaround i'm missing? claus