Sorry but I'm going to drop this plugin because of lack of interest. Mainly my own ;) since I moved to developing responsive sites. Furthermore, I normally activate Jetpack on every site I do and that included a rather smooth mobile extension which can be activated when the site is lacking a responsive theme.
But if I remember correctly, the development version on http://wordpress.org/extend/plugins/wpms-mobile-edition/developers/ has a 'switch theme' menu at the bottom of each mobile page. So if you want to extend the plugin and add a menu that serves your users, please do so. You can fork it or just edit your local copy because there will most likely be no updates to overwrite your work.
Or, if you're interested in taking over maintenance of this plugin, please let me know and I'll add you as committer :)