On the technical side "scary" transclusion has problems with caching and performance. That's why it's unlikely to be enabled at the scale of Wikimedia. No matter how topical or minimal the initial use case may be. Declining for that reason.

Further more, there are content problems with this type of transclusion.

1. As mentioned before, for the user experience it seems more appropriate to provide a link. I don't see how including a full article is useful. If the host page would consist of just a transclusion, then instead of linking to that local page you'd interwiki link to the Wikivoyage page. If it becomes part of a larger host page, the structure of the included page would likely conflict. To give a short introduction, a manual summary, Wikidata description, or Popups/Hovercards seems more appropriate.

2. Copyright. It'll require licensing and attribution information. Something that could be built-in to the transclusion system. But not trivial and needs integration with other citation tools (e.g. when people copy the complete output of this page, attribution to both is now required). There may also be conflicts and license restrictions that do not allow composition (e.g. Wikinews).