I just written a plugin (VVVI), proof-of-concept, that in theory will allow you to integrate X into wordpress, without having to modify X. I’ve tested it on phpbb and mediawiki and seems to work:
https://darkircop.org/vvvi
It’s as simple as adding the URL to X in your wordpress page, and you’ll have X embedded into your wordpress template.
Technically it will fetch X and merge it with the master page (think server-side iframes).