Aikido is an art that takes time. It's an internal art so thus, takes lots of patience. You just can't go around training in as many arts as you can just flood your brain by learning all these techniques at once. You're 17 maybe, and with all those arts under your belt, I think you already have a wide range. Instead of broadening your techniques, I would personally suggest trying to perfect the techniques you already know. An Olympic wrestler has three to four moves that are instinctive to him for every scenario and those are his favorites. Pick out the techniques that best suit you. You know your abilities and talents. Are you fast, are you powerful, are you a good grappler, etc. Some arts weren't just made just to leech off, and aikido isn't one of them. For similiar arts that pretty much place the same emphasis on things like combat TKD and muay thai, leeching off a bit might work, but if the TKD/MT practitioner wanted to learn all the techniques he wanted from say, pa qua, it's not the best decision.
The best thing for a MMA/NHB contest is MMA. That's what it was designed for. However, I understand you trying to diversify but if your mind is already set on competing in MMA, then I suggest you keep on doing that and once your career in MMA is up (everybody has a time where retirement is the answer) then maybe you can learn an internal art on your own. Plus side is, internal arts are basically best for older people. It's easier on the body and it's the time where a lot of people just open up and become great at it.
TMA/MMA - Depending on the school, instructor, and YOU, they can be effective in combat
TMA - For TMA full-contact tournaments (win by KO) or the tap-sparring tournaments, and the other TMA tournament variations
MMA - For MMA no doubt
---------------------------------
May I make one suggestion? Try shuai chiao. Basically, it's combat freestyle, with more of an emphasis on throwing with your entire body, especially locking up and throwing with your hips, arms, and legs. You can try Shoto aka Shootwrestling aka the other names it goes by for MMA which is a combination of freestyle wrestling, sumo, shotokan (maybe, might be another form of karate) and some other stuff.