Proposed solution: When a user enters a QID into Citoid, then Citoid should (or should offer to) generate a reference using the 'Cite Q' template (if it exists on that wiki), with the QID as its first parameter value. When the user enters some other PID, such as a DOI, ISBN, or PubMedID, Citoid should check whether there is a corresponding QID, and if so then proceed as above.
Who would benefit: Editors wishing to cite documents whose metadata is in Wikidata
More comments: Template:Cite Q en:Template:Cite Q is a wrapper for Template:Citation, which it populates on-the-fly using data from Wikidata. Initiated on the English-language Wikipedia, using Lua, it has been developed to be as portable as possible to other projects and to work with minimum setup and translation on those projects. More details in the Phabricator ticket.