As for 3. Haskell already does it now with the IO monad. I can see how having something more specific for effects than the most generic IO type is the next ste

As for 3. Haskell already does it now with the IO monad. I can see how having something more specific for effects than the most generic IO type is the next step on an evolutionary path for languages with an advanced type system. The concern whether or not it is worthwhile then extends to the whole type system.