Just an idea that came up in a discussion: It would be nice if the IDE could show "variations" of source code, where "variations" mean some refactoring that transform source code to other programming styles.

An example:

def sum(xs: List[Int]) =
  xs.foldLeft(0)(_+_)

// this could be transformed to

def sum(xs: List[Int]) = {
  var ret = 0
  for (x <- xs) ret += x
  ret
}

The functional code in the first place is replaced with some imperative code, that does the same thing.