At Luleå Airport there are no customs facilities and the luggage area is directly reachable from the outside world. More than 90% of passengers are domestic and almost all international flights are to EU destinations, but there are also occasional charter flights to and from Turkey. When passengers travel back from Turkey, how are customs checks performed?
If I understand you correctly, Aberdeen was such an airport. There was a telephone by the baggage carousel and anyone with something to declare was requested to use it to call for assistance. (I never once saw it used.)
Not sure about Luleå Airport itself, but most small airports with an occasional flight requiring immigration and customs, simply have an officer or two present to conduct the necessary formalities. There is no need for facilities themselves, just officials to handle the procedures.