A little sidebar... can you say why you prefer the ECO document to be XML/XSL over say something like an MS Word file?
I've got quite a lot of reasons to go with XML files, but below are what I would say the top reasons. I am in the middle of creating and implimenting this, but my initial testing has shown that this is the way we would like to go.
1) We have a lot of off site users who need to access / create ECO's from their laptop or tablet with limited internet access... and by limited, I mean they are most likely tethering into their cell phones, so the connection rate is very slow and to download a MS word or Excel file which could be a few MB can be a hassle. If everyone's computer has the XSL sheet, they can easily download and access the 1 KB XML file and complete their work.
2) Along with off-site users, we have rouge users, who will take our current MS word / excel documents and butcher them to meet there needs, breaking any links or a consistent format. This is easy for them to do because EVERYONE knows how to modify an office document. Not everyone knows how the XML/XSL format is setup or even works, so it shys everyone away from attempting to modify the form.
3) XML files have built in logic, so the document can automatically populate or display infomation based on the users selection.
4) I've seen (have not figured out) that you can do simple EPDM commands such as check in / out or get latest version from within the XML structure. I'm not too sure how to do this, but am aware it is possible.
Not 100% what you are looking for, but it is related. Hawkware Add References tool changes the Paste As Reference process.
I have not tried it yet.