2000 reps sounds an awful lot. Throughout the course of a day, MAYBE, taking into consideration how much strength endurance the thrower has developed in the delts, arms etc.
What if you forsake force which offers minimal mass (4-8lbs)?. The body can adapt to 2000 throws with x amount of weight, maybe not from the get-go but adapt none-the-less. It all revolves around the overload principal.