A good foundation is what you need to start any discipline. The horse should walk, trot, canter when you ask for it. Stop and back when you ask for it. The horse should learn to circle and pick up his inside shoulder to stay balanced. The horse should move off your leg. You should be able to control the shoulder, ribcage, and hindquarters of the horse with your leg. The horse should be soft and supple through the face. All of these make for a good foundation to take a horse in any direction you want. Once you've put many, many miles on your horse, then you can start the process of slowing them, collecting them, and finessing your movements with advanced maneuvers and techniques.
Don't think too far ahead. Each piece of training builds on another piece. If you skip to the "picture" of what WP is, then you will be missing a lot of steps and will have a horse that is representative of the "fake" WP movement.
People will say, "I want my horse to have a slow and cadenced lope". Then they'll get on and pull their horse's face until the horse chugs along on his forehand at a 4 beat.
Did you teach your horse how to balance at a fast lope? Does the horse stay upright in his circles? Does the horse move off your leg to pick up his shoulder? Does your horse have a soft, supple face? Does your horse know how to haunches-in at the walk, trot, and then lope? Does your horse know how to work on a counter canter? Does your horse move off your leg cues?
These are all questions any rider in any discipline would have to consider to get a well-balanced canter or lope. The end result is just to use that balance and collection to slow down the speed, and drape the reins and let your legs/body do the work.