As always, you make compelling argument, I like your passion and drive, and really do appreciate your efforts to drag lesser folk kicking and screaming into the 21st century. Also good to read views of others. Sometiimes things just need to be beaten into shape, however brittle or immalleable...

Suggestion:

In the COWOA fieldset in \includes\templates\MyTemplate\templates\tpl_login_default.php

Whether

<?php (COWOA_STATUS == 'true')) { ?>

should be replaced by

<?php if (($_SESSION['cart']->count_contents() > 0) && (COWOA_STATUS == 'true')) { ?>

to only allow COWOA when customer has products in cart. Otherwise COWOA is visible to visitors proceeding directly to login. Or is this the intention of the original code.