Mark, I think you can try doing that already with the use of iw_watermark_display filter hook.
Try copying that to functions.php of your theme.
function custom_iw_watermark_display($attachment_id) {
// do this in admin only
if (is_admin()) {
// get uploaded file url
$attachment_link = get_attachment_link($attachment_id);
// check if file path points to woocommerce upload folder
if (strpos($attachment_link, 'woocommerce_uploads') !== false) {
// if it does, disable watermarking of this specific image
$attachment_id = false;
}
}
return $attachment_id;
}
apply_filters('iw_watermark_display', 'custom_iw_watermark_display');