Thanks a bunch Alex. With regards to the scenario, in our case, our writers are used to see these attributes pre-populated since it is valid for 90% of all our content. Only for the smaller percentage of the content do our writers actually go ahead and change these values, which saves them quite a few clicks.
1) Create a class which extends the dita extension bundle.
2) Create a new document filter to filter out xrefs and set the attributes.
3) Set the document filter created in (2) within the class created in (1).
Do let me know if there is any alternative to the above steps.
Thanks,
Nathan