I'm only skimming this thread, but I just wanted to note that Rust does support more flexible "self" expressions, though this support is currently limited to Box<Self> (our intention was to support all manner of "deref-able" things, such as Rc<Self> and so forth, but that probably needs an RFC and definitely needs some impl work to see through to completion).
For example, one can do:
trait Foo {
fn bar(self: Box<Self>, ...)
}
and that is legal syntax (even works with trait objects).