I will do this this winter on my X748. I have a small joystick valve that will be mounted in the cup holder area. I bought a new fender deck to use (cut up) as I fit this in place. The valve I got is the right flow rate, but still takes quite a bit so space under the deck!
Mounting on the loader would definitely be possible, but you would not have added benefit of the extra hydro circuits for use with blade...I want to be able to use the front up/down and left/right on the front blade and be able to use the 3pt hitch independently.
As for tying into he system, I plan to remove the factory line between the steering box and the existing SCV. I will tie the new valve in these and then feed the existing SVC from the joystick.. This will give the new joystick first flow for use with the loader. The existing circuits would have secondary power. Should not be an issue as I doubt I would ever use both concurrently.
Keep us posted off you start. I will when I do, but not til it gets cold out! Still working on my new garage.