One thing I've seen is that when you're first learning a langauge and pick up bad habits, they can be really hard to break. I've heard lots of students talk about the problem this causes when interviewing, especially early on. Additionally, for languages like Python, where there is loads of (often excellent) support online it can be confusing/frustrating to have a class teach one method and find answers which are mostly unrelated.
That said, I agree with what was said. Scheme is pretty amazing :)
What is stopping you from implementing those ideas in Python during a first-semester course in CS is that you will not serve your students, as amatsukawa described.
Pretty unambiguous to me. GP had a very thoughtful reply to be clear.
If the desire was to teach idiomatic python, that's totally legitimate. But the decision to whether or not teach FP concepts is in no way constrained by the choice of language.