Do you mean an ODF/.odt editor? Why vibe code them? they already exist. MS Office can open ODF files now. The British government has been using ODF for most files exchanged with the public (e.g. downloads from gov.uk) for many years now with no issues I know of.
The same reason you vibe code a Rust version of SQLite.
The point is that compliance around docx has become a commodity. Now that you have to support 2 formats with your application, that is orders of magnitude more complex.