Dear Patrick,
I would suggest two examples that have already been implemented by the ADOxx.ORG community.
The first example has been presented in one of the ADOxx.ORG Trainings in 2013 and implements functionality for semantic lifting. The example can be downloaded as part of the training materials of the ADOxx Training Days in Vienna, on March 26th - 27th 2013, the package is called
Domain Samples and Development Tools. The whole list of future and prefious ADOxx trainings can be accessed in the
section "Tutorial" of the ADOxx.ORG portal.
The second possible solution is called "Interref Editor" and it has been presented as an implementation scenarion in the "Frequently Asked Question" section of the ADOxx.ORG portal. The solution allows selecting a reference (pointer) by displaying a complex tree containing all the model groups, the models of certain type(s) in each model group and all objects of certain type(s) in each model, including a tree-like structure of those objects (taxonomy-like). A direct link to that post is here:
http://www.adoxx.org/live/faq/-/message_boards/message/87163Although the two solutions have some common concepts, I would favor the second one, mainly because of it's flexibility and ease of implementation and configuration.