There's no clear way to align Flickable item content inside of the the item. For example in some cases ListView content is wanted to be aligned to bottom. It should be possible without changing list ordering like Listview.BottomToTop does.

So there should be some content alignment property to align Flickable item content. It could be horizontal & vertical alignment properties like Text element has:
Flickable.contentHorizontalAlignment
Flickable.contentVerticalAlignment

Or anchor like Item has:
Flickable.contentAnchors

Anchoring might give possibility to anchor content outside the Flickable item. Don't know is that good or bad.

For the listView bottom alignment issue there's workaround to use topMargin depending of the contentHeight:

    ListView {
        anchors.fill: parent
        model: ListModel {
            ListElement { name: "first" }
            ListElement { name: "second" }
            ListElement { name: "third" }
        }
       topMargin: height-contentHeight
        delegate: Text {
            width: ListView.view.width
            text: name
        }
    }