You would need to customize your Shipping Modules so that they do not check if the cart is Always Free Shipping ...
For example, on the Flat Rate flat shipping module in:
/includes/modules/shipping/flat.php
you would see the code:
Code:
// disable only when entire cart is free shipping
if (zen_get_shipping_enabled($this->code)) {
$this->enabled = ((MODULE_SHIPPING_FLAT_STATUS == 'True') ? true : false);
}
To have that run when Always Free Shipping is the only thing in the cart, you need to comment out the test:
Code:
// disable only when entire cart is free shipping
// if (zen_get_shipping_enabled($this->code)) {
$this->enabled = ((MODULE_SHIPPING_FLAT_STATUS == 'True') ? true : false);
// }
Once you have your shipping module running at the same time, you need to determine what the shipping is based on to see if there needs to be further adjustment to the code ...