What's wrong with Muay Thai? I always find it odd that people seem to have biases against martial arts with no real explanation as to why. Look at Kyokushin Karate. It's also good to add boxing to that to add to your arsenal if you choose to do Kyokushin.
Really, though, Muay Thai is the best compliment to BJJ in my opinion. BJJ uses clinching. Muay Thai uses clinching. How each one approaches clinching is totally different, yet they can both be used in conjunction with each other. They fit each other like a matching pair of socks.
Kickboxing is the closest to what you're looking for without being muay thai, kung fu would help a lot too though, particular praying mantis style which focuses on knees/elbows or heron style for that as well. Both will teach flexibilty
Boxing or muay thai for sport, wing chun is good for self defense. At the end of the day if depends on what your looking for out of the martial arts..
Karate is the best striking art to complement BJJ. It shares that Samuri mindset. Nothing is more bi-polar than mixing BJJ with MT, unless you're goal is to compete in MMA.
There is no one magic style that's the best. Otherwise we wouldn't have multiple styles. Just find what you like and what's taught in a legit school in your area and go with it.
Since I currently take BJJ, which works mainly on ground game. Which martial art work best for striking (kicks, punches, knees, elbows, etc.). Preferably not Muay Thai.
