Create a modern style for QtWidgets

I know we have QML to create modern user interface.
But QtWidgets is still used by many users and works very well.
Actually, we have native style for each desktop OS. This is greate, but I think it would be nice to have a single and modern style for all OS.
Of what I know , there is only the fusion style which is OS agnostic. It would be greate to have a second one with modern feature like flat design.