Out of interest what are the positives to aikido? What things could be implemented into other martial artists games? What does aikido do well?
tldr; Wristlocks are under-developed in BJJ. The sophistication of instruction in BJJ is generally low. At least my lineage of Aikido has a framework for formally teaching concepts of movement and control that most BJJ practitioners develop implicitly over years. I think it's a lot more efficient to teach to the end-state goals.
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Aikido's historical technical concepts are sound, but the realistic application has been lost through generations of students who didn't spar. Without getting too deep into the weeds, Ueshiba (the founder) got it more or less completely backwards with his philosophy that competition necessitates creating losers and that the act of losing damages the human spirit. Competitive training creates humble students with robust technique. This realization and its ramifications are why I quit Aikido when I was on the trajectory to becoming a senior instructor.
Narrowly, I get a lot of mileage out of the wrist lock repertoire. BJJ only utilizes wrist compression (think palm to elbow) locks. This ignores internal/external rotation, extension, and all the combinations thereof. You can't execute them the traditional Aikido way that people rightfully make fun of (catching punches with no body control), but in my experience they are as high-percentage as anything else if done from a structurally sound position. I honestly believe that there is room for an expansion of wrist attacks analogous to the explosion of leg locks in recent years. The result won't change the meta-game as much as leg locks, but there's a lot of refinement available.
In a more general sense, the things I find valuable are conceptual. At least in the sub-family of Aikido I trained in, there is a formal pedagogical focus on how to generate and transmit force through the body. This includes ideas of grounding and structure when pushing, efficiently relaxing your body to maximize power, a geometric theory of how to capture your opponent's balance (similar to Judo), a specific vocabulary for footwork and hip movement, and drills and concepts for how to manipulate the tension in your opponent's joints to limit their mobility. All of these these have served me well in BJJ and people find them very useful when I introduce them in classes I teach.
None of this is unique to Aikido per se. The human body only moves in a certain number of ways, and an experienced practitioner of almost any art will learn to exploit them, explicitly or otherwise. However, my Aikido training spoke to these ideas directly from day one with an established teaching method, which greatly accelerated my progression in BJJ. I'm not a world-beater or anything, but I got my purple belt in two years from Romero Cavalcanti and Lucas Lepri so whatever I knew was worth something. This is not to say that I'd recommend that anyone actually go train Aikido in its current state. It would be much better to let someone like me cross-polinate and save the rest of you the time of sorting out the crap (of which there is a lot).