Most web servers already support the ability to combine content from various sources into a single HTML page on the server but Domino does not.
Domino needs this! An example is an HTML page which pulls content from Domino DBs into an otherwise static HTML page. Some might say the page should be generated from the NSF but that's often not possible or convenient, especially when non-Domino graphic designers are involved.
The only workaround I know of it to use AJAX on the client to pull the content together. But this can be a problem for users with disabilities and search engines do not walk the AJAX pulled content.