Sites is a great componenti in Portal for ArcGIS but a complete web site management require a tool to easily publish dinamically news and info.
Actually Sites seems not to allow to embed external pages/component (js, php etc) so the only allowed textual contents are static.
It would be necesary only a a backoffice news/blog editor (title, description, image) and a "news/blog object to drag and drop to the page (i.e column news news gallery with the last 3-5 latest news.
Cheers
Enrico