It would be great if the service being run on a CustomSelector could have some more details about the context of where it is being run. F.ex. that I in the service could get details about what content type the CustomSelector is being used from, and also possible path and ID to the object that is being edited. This can allow us to make smarter services and let the customselector predict better what results to display.
I guess this can also solve this issue here CustomSelector dependant on other input to allow the service to be dependant on other values from the object.