Hi Adrian,
The autoconnect feature, it looks that only works if the interface sta with wlan-sta are present on the wireless file, periodically it will go through the saved networks until it manages to connect.
See this example for the end of wireless file for a 5Ghz network:
config wifi-iface ‘sta’
option device ‘radio0’
option network ‘wwan’
option mode ‘sta’
option ifname ‘wlan-sta’
option ssid ‘NET’
option bssid ‘xx:xx:xx:xx:xx:xx’
option channel ‘157’
option encryption ‘psk2’
option key ‘mypassword’
option disabled ‘0’
Then I have join another saved network this time 2.4GHz
config wifi-iface ‘sta’
option network ‘wwan’
option mode ‘sta’
option ifname ‘wlan-sta’
option ssid ‘NET’
option bssid ‘xx:xx:xx:xx:xx:xx’
option channel ‘6’
option device ‘radio1’
option encryption ‘psk2’
option key ‘Mypassword’
option disabled ‘0’
If you join other network will overwrite the values again but keeping the same interface all the time.
The GL scripts, every time that you click on join a network and success, it will overwrite and create the same interface on the wireless file but with new network name and new password.
For example if you scan and join a network successfully then it will show the new network in both files, if you delete the network from the saved networks file and reboot the router, the router will join automatically the last network as the wireless file stays the same when you reboot the router.
But each time you try to scan and join a network both files will be overwritten again, adding the network on the ssid file and rewrite the wireless file.
So basically the auto connect feature only works if the sta interface is present in the wireless file and then it will go through the ssid file saved networks until success, if you add the correct values of your new network on the ssid file it should be work out of the box for your non-expert user, only you have to at least connect one time to any network to have the interface create on the wireless file
You can go on luci and you will see how GL scripts worked, you will see a new interface wwan part of firewall zone of wan and wan6 and a wireless connection wlan-sta that has been created for the network.
Just modify the values of the wireless network filling your non-expert network user, name and password and let empty the BSSID
If they do not use the GL gui it should work and connect automatically.
Another option to avoid conflicts with the GL scripts is to create another wireless connection with different name than sta , wlan-sta and also different than wwan for the interface.
This is how you do for other routers with only openwrt installed.
Honestly if the router is just intended to be used for travel, the best option is trust in your non-expert user and explain how to join a network from the GL gui, normally they are not interested in the rest of options, only want to have access to the network.
Long story, 
I hope this helps.
Regards.
Victor.
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