That also sound possible but it means working on two webs and deleting mobile webs before every publish. For me that's more complicated.

Right now I'm simply working on the desktop version with the mobile version narrowed so I don't have to worry about it. I work on the single two-variant web and publish. Yesterday I wanted to play around with the size of a graphic on the mobile version so I widened it, played around and then narrowed it again... then went back to the desktop version to continue my work and publish as normal.