tldr:
In the 1950's, doughnut shops were some of the first food businesses commonly open late at night. They became hot spots for police working the night shift since it gave them a place to grab a snack, fill out paper work, or even just take a break.
Rich made some interesting points on developing libraries in such a manner that it doesn't introduce breaking changes (for the calling code). Does anyone here agree (or have counterpoints) to his suggested approach?
All your points (1 through 4) matched with what was looking for. I chose Clojure. It's Lispy, focuses on immutable data (but not necessarily pure functions), has a version (cljs) that compiles to javascript (if you're writing web-apps, its great to write both your front-end and backend code in one langauage). I've broadly found clojure to be a "practical" functional language to work in.
(If it helps, I'm primarily a python/js developer before picking Clojure).
A team's picture gets better when it sees collective participation from a large number of people in the team. Which is why I feel this will beat company LI/FB pages, that are updated by a single person(or a select few)