There currently is no way to change the preview page besides changing the static front page and then having to change it back. However if the user forgets to do this they can easily save the static front page to something else without realizing it.
Also this makes it hard for when you want to view different page templates to see how the theme options will display.
I currently use a button on the page edit that takes you to the customize page and passes along the post id and then place it into the customize.php file on line 168 with get_permalink to display the preview page I wish to view. However this is hacking into a main file which is never a good thing.