I think Uppercase and friends are really interesting (along with all of the other things, of course).
It will be interesting to see if they add metaprogramming capabilities next (allowing anyone to create a class like Uppercase), although I’m not holding my breath.
Yes, this currently exists in 4.1, unless I somehow misunderstand you. I’ve been making heavy use of it with the beta, it’s extremely useful.
Edit: see this SQL made out of the type system: https://github.com/codemix/ts-sql