I think creating new docs file editor is a bit reinventing the wheel. Wouldn't it be better to just create a client which could view and edit existing files with .odt or .ods extensions like in Nextcloud? I tried to attach screenshots but I couldn't... Anyway in Nextcloud you can even create those files and colaborate with others on them in real life. I think it would be much simpler to build. Actually, as Nextcloud is open source, you can just implement their solution!