I doubt you'll ever get FlySmarts on that route, Cirrus isn't part of the main group. I have the same problem on the Munich - Erfurt route. That route can be bought separately as a Round Trip for as low as EUR84, because apparently Cirrus has to offer low-priced domestic German routes. However, if you try to book Munich - Berne the price skyrockets. Lowest I could find was EUR251.