Returning Proxies from Index/IndexMut

internals ideas (deprecated)
2

Is possible to implement a more general Index trait for, say, Vec<T>? I tried a few things but none of them worked:

// Attempt 1
trait Index2<I, R> {
    fn index2(&self, index: &I) -> R;
}

// error: cannot infer an appropriate lifetime for autoref due to
// conflicting requirements
impl<'a, T> Index2<uint, &'a T> for Vec<T> {
    fn index2(&self, index: &uint) -> &'a T {
        self.index(index)
    }
    // The fully typed signature is
    //     fn index2(self: &'s Self, index: &'i I) -> &'a T
    // The compiler doesn't know how 's and 'a are related
}

// Attempt 2
trait Index2<I, R> {
    fn index2<'a>(&'a self, index: &I) -> R;
    // This function declaration is equivalent to
    //     index2(&self, index: &I) -> R;
}

// error: method `index2` has an incompatible type for trait: expected
// concrete lifetime, but found bound lifetime parameter 'a
impl<'a, T> Index2<uint, &'a T> for Vec<T> {
    fn index2<'a>(&'a self, index: &uint) -> &'a T {
        unimplemented!()
    }
}

// Attempt 3 (RFC #192 a.k.a lifetime bounds)
trait Index2<I, R: 'a> {
    // R: 'a means that all the references contained in R must *outlive*
    // 'a, this is the *opposite* of what's required for the Vec case
    // For the Vec case, the lifetimes of the references in R must be equal
    // or *shorter* than 'a
    fn index2(&'a self, index: &I) -> R;
}

// Attempt 4 (Higher Kinder Type constructors?)
// R is a type constructor that takes a lifetime parameter as argument
trait Index2<I, R> {
    // This may work, but we don't have HKT (yet?)
    fn index2<'a>(&'a self, index: &I) -> R<'a>;
    // With this method, I think index2 *can't* return a Copy type like int
}

// Attempt 5 (Vec auto-slicing)
// Is not possible to implement the Index2 trait for Vec
trait Index2<I, R> {
    fn index2(&self, index: &I) -> R;
}

// Implement Index2 for a slice, and just use vec.as_slice().index2(i) everywhere
// If &Vec was automatically coerced to &'a [T], then we could also use vec.index2(i)
impl<'a, T> Index2<uint, &'a T> for &'a [T] {
    fn index2(&self, &index: &uint) -> &'a T {
        &self[index]
    }
}

It can't be done? Or am I overlooking something simple?