I really don't see an easy solution here because we don't track any more the specific fields that have been written (in pre 5.1.x configuration we used reflection to track this). For this to work, you can't rely reading the configuration objects cos they'd bring default values. For your use case to work, when you read the second default, you'd need the XML reader from the 1st config, so that you can only apply those values that have been defined in the XML. I don't see an easy solution here cos staxmapper classes are hidden to be able to do it.

What are you using this kind of set up for? What's the actual use case for having multiple Infinispan XML configurations and rely on this type of overrides? If you can explain the real life use case, maybe we can find an alternative way to achieve what you're after.