Use a FortiExtender 101G connected to a Fortigate 60F as a secondary WAN

I would like to use a FortiExtender 101G to connect to a Fortigate 60F (HA Pair running 7.4.9) and use the FortiExtender as a second WAN connection.

Like this:

FortiExtender (LAN port) <-> Fortigate 60F WAN2 port.

The cell service on the FortiExtender will also have a static IP.

1) Is this setup possible?  I only want to use the FortiExtender as a WAN, nothing else.  So I need to setup the FortiExtender like a regular ISP modem (like "bridge mode").

2) If this configuration is possible, would I configure the static IP of the cell provider in the Fortigate WAN2 port? 

Another wrinkle is that I would have to setup all of this remotely, no physical access to either device.  I would have a non-technical person helping me with connecting the devices.  I therefore need to make sure that I can configure the FortiExtender without the need of connecting a laptop directly to the FortiExtender first.  I need to the configure the FortiExtender WAN port on the Fortigate remotely.