sparkss on "User Profiles Made Easy: Trying to order members by first or last name."

Hello, I am using the plugin User Profiles Made Easy and you are able to view all registered members. Right now the possible values for ordering that work are ID, login, nicename, email, url, registered, display_name, or post_count. I am trying to get it to be able to order by first or last name.

I know it has to do with this part of the code

// Setting up order data
        if (in_array($this->profile_order_field, array('nicename', 'email', 'url', 'registered')))
            $orderby = 'users.user_' . $this->profile_order_field;
        elseif (in_array($this->profile_order_field, array('user_nicename', 'user_email', 'user_url', 'user_registered')))
            $orderby = 'users.' . $this->profile_order_field;
        elseif ('name' == $this->profile_order_field || 'display_name' == $this->profile_order_field)
            $orderby = 'users.display_name';

  elseif ('firstname' == $this->profile_order_field || 'user_firstname' == $this->profile_order_field)
            $orderby = 'users.user_firstname';

        elseif ('ID' == $this->profile_order_field || 'id' == $this->profile_order_field)
            $orderby = 'users.ID';
        else
            $orderby = 'users.user_login';

And this part

c=b.addMenu({title:"Multiple Profiles / Member List"});
									a.addImmediate(c,"Group of Specific Users", '[upme group=user_id1,user_id2,user_id3,etc]');
									a.addImmediate(c,"All Users", '[upme group=all users_per_page=10]');
									a.addImmediate(c,"All Users in Compact View", '[upme group=all view=compact users_per_page=10]');
									a.addImmediate(c,"All Users in Compact View, Half Width", '[upme group=all view=compact width=2 users_per_page=10]');
									a.addImmediate(c,"Users Based on User Role", '[upme group=all role=subscriber users_per_page=10]');
									a.addImmediate(c,"Administrator Users Only", '[upme group=all role=administrator users_per_page=10]');
									a.addImmediate(c,"All Users Ordered by Display Name", '[upme group=all order=asc orderby=display_name users_per_page=10]');
									a.addImmediate(c,"All Users Ordered by Post Count", '[upme group=all order=desc orderby=post_count users_per_page=10]');
									a.addImmediate(c,"All Users Ordered by Registration Date", '[upme group=all order=desc orderby=registered users_per_page=10]');
                                                                a.addImmediate(c,"All Users Ordered by First Name", '[upme group=all order=desc orderby=first_name users_per_page=10]');
									a.addImmediate(c,"All Users showing User ID", '[upme group=all show_id=true users_per_page=10]');
									a.addImmediate(c,"Search Profiles", '[upme_search operator=OR]');
									a.addImmediate(c,"Search with Custom Field Filters", '[upme_search filters=meta1,meta2,meta3]');

This is the shortcode I'm using on the page

[upme_search autodetect=off filters=graduate] [upme group=all view=compact width=2 order=asc orderby=first_name users_per_page=8]

As you can see I have already messed with the code trying to add first name as an option to order as well. I have tried all kinds of combinations so far, but have had no luck. Any help in resolving this would be much appreciated. Thank you.