I've considered setting up something for handling combat, and make a simple frontend/manager via C++. Are there any existing rulesets? :sniper:
As far as I know, you're welcome to use the NationStates XML (http://ns.goobergunch.net/wiki/index.php/XML_feed) information in some third-party offsite location, but there won't be a combat option added to this game.
Try the NationStates 2 forum for some suggestions.
(As always, the sniper smilie adds enormous credibility to your post)