To be honest I don't fully understand the question. What you wrote sounds like we have something like this already. Or did I get this wrong?
On a very high "user experience" level unrelated to MediaWiki I do have a suggestion: You could do it similar to how "like" features in social media clients are implemented. Clicking such a "like" button feels like it's immediately done. But in reality the job is not done yet. There is still a request going on in the background, which might even fail.
In other words: The client-side immediately gives the user a response that is most likely to happen, without actually knowing if it happens. In case of a later server-side error the visual response is updated to let the user know.
When an element on a page is edited and the user clicks "save"; the client-side already knows everything, doesn't it? It could update the old rendering with the new information and present that as if it is already saved.
That's more or less what React frameworks are about.
What you probably don't want to do is to re-implement complicated rendering pipelines on the client-side. In this case you might need to use a spinner or other kind of placeholder.
Best Thiemo