It was basically this - and to be clear this is not a shortcoming of QML. As you said, splitting the logic layer from the UI is a good idea - but the choice for us to be building apps in QML without a logic layer under it required a lot of weird solutions that could've been easily addressed if we'd been doing C++ and Qt. But our team were Javascript developers, the team we were partnering with were Qt devs, and someone had negotiated this solution and we did the work.