If the Expediton's brake controller is like the F150 and Superduty brake controllers, it won't be an inexpensive upgrade.
You will have to replace the master cylinder and some other electronics.
I have the integrated brake controllerr in my 2005 F250. It's a great controller. When I bought my 2008 expedition, I installed aProdigy. Works as advertised, but not as seamless as the integrated unit in my F 250.
I'm still hoping for towing mirrors. Hopefully, the next generation Expeditions will keep the same door design so if Ford does release towing mirrors, I cam get some for my truck.