Implement a way to have each instrument view specified as a .qml file, having each one of those installed in a given path (ex: /usr/share/minuet/qml-plugins/instrument-view/) and then loading them dynamically.
We can by now use a QQControls2 TabBar to show the available instruments
The pianoview would be one of those plugins
It doesn't need to be a proper QML plugin as described in http://doc.qt.io/qt-5/qtqml-qmlextensionplugins-example.html
It's just a bunch of qml files that are stored in a given path and are loaded dynamically with the Loader element.
By now, I'd just try to create two simple plugins (only with a rectangle inside) and having them loaded into Minuet