A really easy way to "configure" this MOD could be like this:
Edit the file ~./index.php and coment this lines
<div class="lcol">
<img src="./images/new_ticket_icon.jpg" width="48" height="48" align="left" style="padding-bottom;">
<h3>Open A New Ticket</h3>
Please provide as much detail as possible so we can best assist you. To update a previously submitted ticket, please use the form to the right.
<br /><br />
<form method="link" action="open.php">
<input type="submit" class="button2" value="Open New Ticket">
</form>
</div>
That delete the form to create tickets, so you can create a ticket from staff panel with the email for your costumer and then send a message with number of ticket, and the costumer can login with his mail and the number that you sendit. Like a password.
If you need to delete the link of "New Ticket" just edit the archive ~./include/client/header.inc.php and comment this line:
<li><a class="new_ticket" href="open.php">New Ticket</a></li>
I know this is not enterily what you want but is the 2 minutes way to do something like that.