wireless networking - Assigning same MAC Address to access points

I am working on a mobile application project which works on a local wireless network located on multiple different geographic locations(some supermarkets).

In that for detection of that particular store for further processing we require MAC ID of that WiFi router, this works fine for a distance, But on vertical mutiple floors lets say 5, its not feasible,So for that we are planning for Access Points to extend it,

Now I would like know that can we configure the Access points with the same MAC address so that when app connects to network it can easily identify which store it is in. (I don't think it is possible but its a random thought)

or

we have to store all the MAC IDs of all the network equipment's to our DB for detection for that particular store.

or

we have to use the Unique SSIDs.

So what is the best solution.

Note: We are using the MAC ID (BSSID) as they are unique and can be accessed easily using some smartphone APIs. and local network has their local server which provides product details and other data to the device.