Allow call to QWindow::fromWinId() for QML Window object

I'm developing a QML based application (with C++ integration), and I'd like to find a way to make an externally launched application internal to my application.

Solutions I've found for tracking an external window is retrieving the QWindow object via QWindow::fromWinId() (looks like I can take ownership of it with QWidget::createWindowContainer() as well, and possibly change how it's layered). There appears no possible way to do this in QML. My solution would to overhaul my entire application to a QWidget based application, which seems to be a step backwards...

What would be very convenient, is if the Window object in QML (which inherits QWindow anyways) can call the fromWinId() function, then I can possibly make the external app part of my QML application internally without having to rewrite everything widget based.

That, or some QML global function that returns a QML Window object instead of QWindow object.