Hi,
I agree that an API to assign the splash url would be ideal, that's not the case today.
That being said, the way I've accomplished this is by using the access points MAC address. This only works if you have one splash page per network, which is the most common scenario.
I use a custom JS library I'm writing to handle these types of use cases:
https://dexterlabora.github.io/meraki-service/module-Custom.html#.getNetworkIdForDeviceMac
meraki.getNetworkIdForDeviceMac(orgId, deviceMac)
.then(response => {
console.log(response);
}
// Network ID
// L_123456789012345
With the network ID, lookup the name/details, then apply custom policies to the client or deliver location specific content.
btw, are you really serving 15 SSIDs on the same AP? This is not a best practice if so. I would consider dynamic splash pages on a single SSID, where possible. Unique SSIDs should only be advertised when they require different association types (open/WPA2/Ent). This will reduce interference by lowering broadcasts, etc.