Maybe have a look at Rendering data from Entity model to the inspector using DataSource
The thing is that it’s not supported very well at the moment. Fortunately references to arbitrary nodes in node properties should be possible with the next release (2.3), see https://github.com/neos/neos-development-collection/pull/102. Meaning you only need to write the data source for being able to select the domain models, whereas now you have to also fetch them manually from the stored identifiers.
Additionally there is a non-public API approach to use domain model logic called content object proxy. However it has some design drawbacks and needs quite a bit of custom handling, see https://github.com/neos/neos-development-collection/pull/20