I've been searching here and there for it, but I can't seem to locate an Open Document Format Datatype. This would be the format that OpenOffice/LibreOffice uses for it's documents.
The best I can do for you is this:
http://internetpages.bravepages.com/docdatatypes/I don't know whether the author is still active, but it certainly hasn't had an update in a long time (and there's no ODF support)
Datatypes are one of the coolest things about the newer versions of AmigaOS, but I'm not sure what exactly would be involved with creating an ODF for it. I haven't even been able to find someone asking the question. I would love for any word processor that utilizes datatypes to be able to support opening and saving of ODF.
Most word processors don't support using datatypes to load/save text.
The datatypes on the above links are subclasses of text.datatype, so you'll lose all the formatting.
Subclasses of document.datatype are doable and would keep the formatting, but there's no way of doing anything other than viewing them in MultiView.
What I think you actually need is a WP which supports ODF.