Intercept the coupon types and do what you will, add or remove as you see fit.
[php]
<?php
function webdav_newcoupon_type ($discount_types) {
// Custom Code here
return $discount_types;
}
add_filter (‘woocommerce_coupon_discount_types’, ‘webdav_newcoupon_type’, 10, 1);
?>
[/php]