I’m not familiar with oBIX, but it looks like it’s just an XML interface, but with a standard vocabulary, right? In that case, it’s probably a good idea.
On the other hand, I’ve noted in the past that the XML interface you’ve got is really over-permissive and doesn’t exactly conform to XML standards, so if you do want to go to a standard like oBIX, you’ll probably have to make XML conformance a lot more strict…