I've yet to install a controller, as all my towing with the Ranger has been with surge brakes.Great call on the brake controller, it's a bummer that it doesn't come with the tow package. It doesn't look too bad to install, but I'm terrified of breaking trim clips and you gotta move a lot of trim for it (I don't unsderstand why it has to wire to the third brake light? Seems like all that info must be available near the fuse panel ...).
But this is my understanding. It is possible to tap the brake light signal at the BCM under the dash. The pin has been identified here. But the Ford kit is designed to not have to tap a wire. It's plug Ts in at the point where the wiring harness plugs into the CHMSL. Using plugs is probably more foolproof than tapping.