XML to both ODF and OOXML conversion

Hi,

Our system should generate both formats from custom XML to ODF and OOXML

Need advice about best workflow

option 1 is XML -> ODF and XML -> OOXML (independent XSLT for both formats)
option 2 is XML -> intermediate format (maybe as mixed namespaces from
ODF, OOOXML, XHTML, MathML) then two XSLT for ODT & OOXML
option 3 is XML -> ODT -> OOXML (look like not so simple as expected,
3rd party XSLT see http://odf-converter.sourceforge.net/ still not
work as expected - too many bugs)

i guess that i am not single person who have this problem - what about
your experience?

with best wishes,
Slav