How to write "Meld-like" plug-in for odf and xml?

Hi,

bzr seems ideal for text writers due to its flexible and easy workflows, except that there is, as far as I know, no support for "binary" text formats like OpenOffice and Word. It would be nice with something like Meld to view differences between versions and a diff3-plug-in to handle conflicts.

Maybe it could be done with OpenOffice's merge functionality (requires python uno I suppose). Or maybe something else is better, like a more text-based approach (no dependence on python uno).

What would be the best approach to make a plug-in for:

1) XML-documents where writers can focus on text content rather than markup (fx FreeMind documents).

2) OpenOffice files. (Open documents are zip archives with several xml files in them.)

3) Other file formats that OO can handle (doc, rtf, xls)

Any existing plug-ins or python modules that could be useful, cloned or modified?