matching mdrpi elements in attribute filter? xpath?

[Peter Schober]

Just saw the announcement about 2.4, great. I wanted to ask what the
chances were of getting something into 2.4 (or what your thoughts are
on this generally) that allowed matching on
mdrpi:RegistrationInfo/@registrationAuthority attributes in the
attribute filter.
Maybe having a generic facility to evaluate xpath expressions would
help with this and many other cases?
If others find that useful I can at least add a case in Jira for that.
-peter