I am installing what the OP is asking about currently on my b8200. Because my tractor is not one they sell a kit for I am having to do some work to get it to work with finding the fittings to connect to the factory hard line connections as well as getting custom hoses to fit where I want to put the valves.
To convert the rear remote kit kit to work as a 3rd function as well I ordered it with the joystick like you mentioned and put elbows on one of the valve outputs instead of the quick connects, then ran the lines to the front.
I was a bit disappointed in the switchbox that is sold with the kit, they did well with waterproof connections in the harness, but the switchbox seems rain resistant at best and only when mounted in the right orientation. I am planning to use it until I get around to making a better one.
If you need any more information just let me know and I will do what I can.