Regarding implementation, XWiki is fully extensible and it would be enough to implement a ResourceReferenceTypeParser role with a sip or uri hint. And a XHTMLLinkTypeRenderer role with a sip or uri hint for the rendering to HTML.
See https://rendering.xwiki.org/xwiki/bin/view/Main/Extending/#HAddinganewLinkType for more
EDIT: I’m not sure how it would appear in the WYSIWYG editor though, I hope it’s automatic, cc @mflorea