Proton has started making Proton Docs and that ecosystem which is great but the FOSS world already has the likes of LibreOffice and others. Integrating them into Proton would show Proton cares about FOSS but also gives Proton Users the option to use other open-source software right into Proton's Web UI.
Adding the option to open docs files in a web LibreOffice Editor would be amazing. I think Proton can and should build their own Docs and etc ecosystem but they should also integrate others that are FOSS, ethical and privacy minded.