Which elements of the Evolved Packet Core are necessary to retain WLAN connectivity?

Let's say I have a small town that wants to retain local LTE services when it is disconnected from the WAN. In order to have local operation, does it need a HSS? SGW? PGW? ANDSF? All of these and more? etc. I understand the basic definitions of each component of the EPC but I still can't see how it all fits together in such a scenario.