// Replace hierarchial taxonomy entry with radio field
class exmp_tax_radio_field {
    function add_theme_box() {
        add_meta_box('theme_box_ID', __('Theme'), 'your_styling_function', 'post', 'side', 'core');
    }
    function add_theme_menus() {
        if ( ! is_admin() )
            return;
        add_action('admin_menu', 'add_theme_box');
    }
    add_theme_menus();
    // This function gets called in edit-form-advanced.php
    function your_styling_function($post) {
        echo '<input type="hidden" name="taxonomy_noncename" id="taxonomy_noncename" value="' .
                wp_create_nonce( 'taxonomy_theme' ) . '" />';
        // Get all theme taxonomy terms
        $themes = get_terms('theme', 'hide_empty=0');
    ?>
    <select name='post_theme' id='post_theme'>
        <!-- Display themes as options -->
        <?php
            $names = wp_get_object_terms($post->ID, 'journal_issue');
            ?>
            <option class='theme-option' value=''
            <?php if (!count($names)) echo "selected";?>>None</option>
            <?php
        foreach ($themes as $theme) {
            if (!is_wp_error($names) && !empty($names) && !strcmp($theme->slug, $names[0]->slug))
                echo "<option class='theme-option' value='" . $theme->slug . "' selected>" . $theme->name . "</option>\n";
            else
                echo "<option class='theme-option' value='" . $theme->slug . "'>" . $theme->name . "</option>\n";
        }
       ?>
    </select>
    <?php
    }
}
$exmp_tax_radio_field = new exmp_tax_radio_field();