Provide a mechanism to annotate QML declarations

Currently, the only way to change the UI declaration, layout and definition based on a precondition like e.g. the screen resolution is to either encode in states;

State {
   name: "QVGA"
   when: width==320 && height==240
   PropertyChanges { ... }
}

or by using an exposed object to compare and declare the right value inline - e.g. for languages;

Image {
   source: Qt.lang == Qt.it || Qt.RTL ? "foo_it_rtl.png" : "image.png"
   ...
}

One idea would be to provide an annotation mechanism in QML;

Image {
   source = "image.png"
   source[lang=it, RTL]: "foo_it_rtl.png"
   width[default=123]: height+10
}

However, the syntax clutters QML and detracts readability.