If you will ever begin development on this feature, you may take my partial implementation from my project:

https://github.com/kontalk/tigase-extension/blob/master/src/main/java/org/kontalk/xmppserver/ExtendedAddressing.java

For now it only implements "to" recipients, but it's a start. Feel free to use the code in any way you like, consider it donated. Although, I saw that Tigase went under some major refactoring due to the new kernel/beans infrastructure so the code may not be valid anymore.