Transparent mode WAN and LAN on same network

Hi folks,

perhaps this is some kind of a strange question:

If I had a LAN-Network which is connected to a FGT in NAT mode and then to a router, finally to the internet, is it possible to use an additional Fortigate in transparent Mode between the LAN and the Fortigate in NAT mode.

That way:

LAN <-> FGT in transparent mode <-> Fortigate in NAT mode <-> Router <-> Internet?

The lan-port of the FGT in transparent mode will get an IP from the local network, thats clear.

But which IP will I have to assign to the WAN-Port of the FGT in transparent mode? Because the LAN and WAN port of the FGT in transparent mode, will be on the same network.

LAN 192.168.10.x -> Gateway (=Forti in NAT Mode) = 192.168.10.254

So the transparent FGT will be in the 192.168.10.x  network (both interfaces LAN and WAN).

Is it possible to do something like this?

Edit: In fact, the more I think about it, it can only work that way. (LAYER2)

Thanks!