> I want the editor to look at temporary buffers served up from the language server and have the code be “written” by sending the temporary buffer back to the language server which handles writing it out to files itself.

I don’t think any editor would want to accept this workflow. The biggest issue is that writing is reputation-critical, if the editor writes to the wrong place, or it fails to write when it should have written, then users lose their work which makes them very unhappy. So the editor has to take responsibility for doing the writing, and that is the user’s mental model when they save their work.