Here's what they do to MNK.

1) Change the CD of Riddle of Fire/Brotherhood to 120 seconds. Extend the duration of Brotherhood to 20 seconds and have it apply to all damage.
2) Remove the GL requirement of Tornado Kick and instead have it be something that can only be used every 3rd refreshing of GL (This also applies to refreshing caused by Riddle of Earth and Anatman)
3) Change Anatman to only grant GL stacks every 3 seconds, regardless of server ticks and lower the CD to 30 seconds.
4) Change SSS into an oGCD that can only be used after a successful Tornado Kick and grant 10 seconds of True North upon its execution with no slow effect.
5) Either remove the True North effect from Riddle of Earth entirely, or reduce it down to 10 seconds at the most.
6) Remove the Fist Stances and untie GL4 from them. They offer nothing to the class and are fluff that can be removed entirely. They can also make the fist stances into just weaker versions of Riddles that change to riddles later on, with Fist of Wind becoming a trait to increase movement speed and Riddle of Wind being the trait to unlock the 2nd Should Tackle.
7) Have Brotherhood naturally generate 1 Chakra every 3 seconds for its duration while also still maintaining the extra chance to earn them from allies.
8) Change Deep Meditation into a 100% guaranteed chakra on crit.

Just some of my own personal adjustments to MNK. Take from them what you will, I feel that they would be pretty balanced, all things considered.