I'm not sure if this was intended in jest, but it's a bit interesting to treat it seriously so I'm doing so... I think it would not be a very good choice to implement a dynamic language in Haskell, because what it makes flexible is choice of Haskell type, and you likely don't want to tie implemented-language type to Haskell type like that. It would seem more likely to be useful if you wanted to host a dynamic language within Haskell.