I'd be interested in such article. I also worked on a similar project lately where I had to communicate with payment gateway using web services. It turned out it cannot be done with Domino alone because Domino cannot present SSL certificates when consuming web services. You can read about this issue here: https://www-304.ibm.com/support/docview.wss?uid=swg1LO50384 . Even though the site says "The problem will be fixed in the next release of the product" nobody at IBM can answer when it will be fixed (if ever).
Since IBM wasn't interested in implementing such a feature, I used PHP to communicate with web service. PHP and Domino then exchange data through simple GET requests (REST style). PHP part is invisible to users.
I know it can take a lot of your time to write a detailed article, but you've been quite quiet lately, haven't you? ;-)