I don't know if this is an option for you, but one thing an instructor of mine did in your situation was get the big, strong person tired as hell. Have them do bodyweight exercises (push ups, jumping jacks, burpes, etc...) until they are fatigued and then keep them fatigued (key point! They must never fully recover). When fatigued, they simply don't have the energy to muscle someone around. For safety, have them work with more experienced, level-headed folks who won't take advantage of the situation and protected them during throws.