you can create a new rendering extension by copying the existing csv one and calling it something else. Then you can even hide it so that it can only be used by this one report schedule and not shown to the users. I believe the BOL documentation talks about creating one where the default print orientation is portrait and the other is landscape.

As an example, my users only see the rendering extensions to export to xls and pdf, but ones like the image one are still there because the rsclientprint utility needs it to operate properly.

-Luke.