I believe gymnastics is one of the most overlooked forms of training for strength athletes. In the last few years, athletes like GSP or training forms such as crossfit brought the importance of gymnastics to the fitness media. I think gymnastics is one of the best things to do for cross training, building functional strength and becoming more athletic.
Years ago when I was a Judo instructor, I sparred against a student who was about my size and was a white belt but had a good amount of BJJ experience and some stand up nogi grappling experience. Even though this student was a white belt, I was pushed to my limits and he challenged me more than some of the very elite black belts I grappled against. I was able to throw him but it was a the biggest struggle. Frankly I was quite worried I would get my butt kicked. I was so shocked and intrigued by his ability to generate strength, agility, grip strength and explosiveness. He did not look like a guy that lifted weights so after class I just had to ask him what he does for his strength training. He was super cool and took me to the next room and showed me his ring routine which included muscle ups and various ring exercises along with drills that are regularly part of a gymnastic program. This was at a time crossfit was just starting up a and muscle ups was not really an exercise known outside the gymnastic community. I added these exercises to my training and my athleticism and ability to generate strength during sparring seasons and skyrocketed.
In Eastern Europe, combat athletes cross training in gymnastic is a very common thing. They understand the benefits and they use it as a huge training part of their regimen. This may be one of the major contribution to the Russian, Azerbaijani, Bulgarian, Turkish, Georgian, Chehen athletes successes. I am sure there are many other things that contribute to the success of these athletes but they have been using gymnastics for a very long time in their training. I knew of Azerbaijani Judo olympic gold medalists performing ring workouts regularly long before the crossfit games even started.
Any exercise that requires to move your body through space is a great way to build functional strength. In most sports we are moving with speed, momentum in 3 dimensional planes so I think it is very important that we train in a very similar fashion. I still believe statinary lifts stuch as squats, deaflifts, bench pressing and other forms of main stream training methods are necessary. I just belive that we also have to do forms of trainings that require us to move through space with a good amount of speed, similar to gymnastics.
Gymnastic requires so much athleticism. Exercises like back flips are one of the most demanding exercises that requires you to be athletic. So, what other way is better than developing athleticism than doing move that requires athleticism? I highly recommend that you use gymnastics and slowly incorporate it in your training program. Muscle Ups, handstand walks, back flips, levels on rings are a good place to start. Make sure you consult a doctor before you train and that you work under a certified gymnast who can teach you how to do these moves/exercises properly.
Check video below which is a footage of GSP cross training in gymnastics.