There will be no stylesheets.
Use style.qml to define all properties. That in essence is your 'style sheet'. I will not integrate the other stylesheets as the introduce more problems than they solve.
Its quite trivial to set a property for both orientations
property int buttonH: b_orientation ? 50 : 60
This for example will make the property button height change based on the orientation. Is there some other qml issues you are having defining the style?
trust me, stylesheets become problematic!