With MyWi in infrastructure mode bridged and natted.
The issue that you’re going to run into is actually having the iPhone produce a wan input for the router..
So what you can do is using a Mac and an iPhone that is tethered and using iphone USB networking to the GPRS data connection (the personal hotspot)
You will now configure the Ethernet port as a data connection bridge from the iPhone to an Apple AirPort Extreme.
The iPhone USB networking environment will show you which IP address (this is the Data address assigned on the IP side by your carrier) that you’re going to put into the airport extreme (using the AirPort Utiility) as the router address.
The ethernet connection for the Mac book to the WAN port will provide you with the data connection. From there you can use the other for ethernet ports to distribute data via rj45,
While the Mac is using iPhone USB networking for its data connection you can also serve up infrastructure 802.11 connections using mywi on Bluetooth or Wi-Fi to other Bluetooth or Wi-Fi enabled devices as DHCP clients, they would just need to be subnetted differently which the software has a solution for.