From the description, I'm imagining something like a "scrapbook" system, where I'm browsing various existing content pages on a topic, and I can highlight a chunk of text (or files), and select "copy to my story", which will add that paragraph to my page, perhaps as a blockquote, with a link going back to the origin. I could then also intersperse the chunks, with my own text and files.
Does that come anywhere near, to what you intended? :-)
E.g. My Story could look something like this, in the abstract:
This is my travelogue. I first visited the town of Foo.
< insert [[wp:Foo (town)]] intro sentence and image, oldid 12345 >
I met a nice cat there
< insert [[c:File:Cat sleeping on a statue in Foo]] >
I visited the church described in the famous book ''Bang''.
< insert [[s:Bang/Chapter_22#3]] paragraph 3, oldid 5432>
Wikivoyage had warned against a visit to the abandoned mine, which I should have listened to...
< insert [[wikivoyage:Foo#Stay safe]] entire section, oldid 765765 >
Many adventures were had, whilst escaping that Lovecraftian catacomb. [...]
Or, to put the question in a slightly different way... Are there any example or similar interface systems that you have in mind?