> This last option gives us the worst of both worlds: it further establishes OOXML as the standard format, and it further establishes MS Office as the only office suite that supports the standard format perfectly.
> (With "OOXML", I mean the format that MS implemented, not the one that was specified as an ISO standard.)
In reality the most correct approach is DWMD (Do What Microsoft Does).
Seriously. Nobody is ever going to follow the OOXML spec. It's just a joke of epic proportions. The only really correct thing to do is maintain compatibility with Microsoft software. Other people will do the same and then that will achieve the highest amount of interoperability from this 'worst of all worlds'.
Trying to fight and be 'correct' on OOXML just means that people will be less able to use OO.org. It effectively becomes a anti-feature.