Sometimes i've thought about grappling as dealing with the hardest type of external load, another person. This is because it is constantly changing and purposefully trying to get to your weakest angles. when big strong guys first start training, you notice that they are always trying to grab the other guy and forcibly move him around. good guys at BJJ generally move themselves around more relative to the guy to obtain an optimal angle.
the key point learned over time is body awareness, and i feel that gymnastics helps with this very much. being able to control your own body and move it accordingly allows you to use the most advantageous position to get tasks done (even when you're in a leverage disadvantaged position like a planche).
aside from that, i feel that if you're going to use weights, you should just do the tasks that resist extremely high amounts of force. thus deadlifting and squatting are prime candidates since the possible weight you can use in these lifts causes much more force to be generated than many other lifts. likewise OL may be a bit less weight than DL and squat, but the acceleration aspect increases forces as well.