Did you consider using QtQuick.Controls ?
I use QtQuick for other interface part - for scrolling history list of this line edit. But this list build logic is little complex and is not suitable for QML. Or better say - on C++ it is implemented easier. I confess following religion - QML/QtQuick only for views, but Qt/C++ for models and business logic. Therefore QLineEdit is most suitable solution. It works fine. But how force validator pass "." instead of "," in this edit only?