While that works for native English speakers working on Latin-based documents, an internationalized syntax that supports any type of document reference (figure, table, algorithm, listing, equation, page number, heading, bibliographic entry, ad nauseum) would likely have a wider impact and greater adoption.
Certainly, different editors will have different ways to present the information. That’s a benefit to using a plain text format, not a deterrent to having a standard syntax. A standard eases porting documents from one editor to the next (i.e., no translation software needed).
Here’s an animation of how I envision the “tooltip” working in KeenWrite:
In my mind, a cross-reference and a citation are the same thing: they are both ways to reference an item. While it would be convenient to inline the citation metadata, there’s a whole ecosystem of tools dedicated to bibliographic references that would be unusable (such as JabRef, Zotero, and ConTeX/LaTeX/LuaTeX/SILE modules). Further, it would require two new syntaxes (one for internal document references and a separate one for external references), which is additional development effort for parsers.
For myself, I don’t see the benefit: there’s already a syntax for handling bibliographic references. Why not keep that externalized? Let the renderer handle linking the file and the document, rather than the syntax.
To me, that’s a presentation issue, best left for the renderer.