A very short article may be replaced by translating a longer article.
When the user visits a page which is a stub, we can provide an option to create the article based on a translation.
We should suggest that only if a reasonably long (or maybe good article/featured) article is available in a language the user knows.
Similarly, from inside Content Translation, we are currently discouraging the creation of a translation if the article exist (not showing suggestions and warning when the user looks explicitly for it). We can be more inviting when the article involved is a short stub.
One of the complications discussed is that identifying a stub across languages is not easy due to the lack of consistent templates. We need to investigate if Wikidata can help with this.
The focus of the current ticket is on inviting users to expand stubs, the support needed for the translation editor to support expanding existing articles is captured in T114850: Add support for translating pages where target page is not empty