Yes, but now you are requiring people to know both Python AND Haskell/StandardML/Whatever in order to maintain your Python app. Python is not just a "base" lan

Yes, but now you are requiring people to know both Python AND Haskell/StandardML/Whatever in order to maintain your Python app. Python is not just a "base" language, it's also a set of patterns for how you go about writing code in it. Conforming to those patterns to some degree makes for (subjectively) nice code, and (objectively) easier to understand code because of the familiarity.