Way of the Cobalt Soul with a better Extract Aspects (now Lost Prospect Method), a more mystical/less redundant Mystical Erudition (now Mystical Enlightenment), a more forceful Extort Truth (now Exact Axiom) and a new Debilitating Barrage (now Harmonic Convergence).

Lost Prospect Method

Beginning at 3rd level when choosing this tradition, you can accurately strike pressure points to extract crucial information about your target, granting you insight about their abilities. Whenever you hit a creature with one of the attacks granted by your Flurry, you mark them as analyzed for 1 minute. The Analyzed condition ends early if the target dies, you die, or you are incapacitated. 

You can use your reaction to gain a bonus to your AC and Saving Throw equal to half your proficiency bonus (rounded down) against an analyzed creature's attack or spell, and you can immediately make a melee attack against that creature as part of the same reaction whenever the attack misses you or you succeed on the saving throw.

You learn one of the following attributes about the target: Ability Scores, Armor Class, [Conditions & Condition Immunities], Creature Type, [Damage Vulnerabilities, Damage Resistances & Damage Immunities], and Senses. As a bonus action on your subsequent turns, you can learn one additional attribute about the target if it is within 30 feet of you, and behind less than 2 feet of rock, 2 inches of any metal other than lead, or a thin sheet of lead.

If the creature is not hostile to you or it's speed is 0, you can use this feature by touching the target and expending 1 ki point instead of hitting it with Flurry.

Exact Axiom

At 6th level, you can hit a hidden cluster of nerves on a creature with precision, temporarily causing them to become mentally malleable. If you hit a creature with an unarmed attack, you can spend 2 ki points to cast the Suggestion spell on this creature without providing material components. 

If the creature is not hostile to you or it's speed is 0, you can use this feature by touching the target and expending 2 ki points instead of hitting it with an unarmed strike.

Mystical Enlightenment

Beginning at 6th level, you’ve undergone extensive training with the Cobalt Soul to expand your keen insight of others to a preternatural level. If you spend 4 ki points over a period of four days or fewer while actively observing or interacting with another creature, you can learn one language it knows, and you gain proficiency with one skill, tool or weapon it knows, provided it speaks and writes that language, or uses the specific skill, tool or weapon in your presence during the ki expenses. 

 If you already have proficiency in the chosen skill or tool, you can instead choose to double your proficiency bonus for any ability check you make that uses the chosen proficiency. You lose the chosen language or proficiency whenever you use this feature to copy more language and proficiency than you can copy with this feature.

You can copy an additional language and an additional proficiency  (with the ability to double the bonus of an existing or obtained proficiency) at 11th and 17th level.

Mind of Mercury

Starting at 11th level, you’ve honed your awareness and reflexes through mental aptitude and pattern recognition. Once per turn, if you’ve already taken your reaction, you may spend 1 ki point to take an additional reaction.

Mystical Enlightenment (Additional)

If you spend 4 ki points over a period of four days or fewer while actively observing or interacting with another creature, you can learn one language it knows, and you gain proficiency with one skill, tool or weapon it knows, provided it speaks and writes that language, or uses the specific skill, tool or weapon in your presence during the ki expenses. 

 If you already have proficiency in the chosen skill or tool, you can instead choose to double your proficiency bonus for any ability check you make that uses the chosen proficiency. You lose the chosen language or proficiency whenever you use this feature to copy more language and proficiency than you can copy with this feature.

Harmonic Convergence

Upon reaching 17th level, you’ve gained such an understanding of the interconnectedness of all things that you can promptly influence the action of a creature with whom you have aligned your ki. When an analyzed creature within your reach makes a damage roll, an ability check, or a saving throw, you can use your reaction to roll your Martial Arts die and subtract or add the number rolled to the creature's roll. You must choose to do so before the roll.

After using this feature on an analyzed creature, the creature is no longer considered analyzed.

Mystical Enlightenment (Additional)

If you spend 4 ki points over a period of four days or fewer while actively observing or interacting with another creature, you can learn one language it knows, and you gain proficiency with one skill, tool or weapon it knows, provided it speaks and writes that language, or uses the specific skill, tool or weapon in your presence during the ki expenses.

If you already have proficiency in the chosen skill or tool, you can instead choose to double your proficiency bonus for any ability check you make that uses the chosen proficiency. You lose the chosen language or proficiency whenever you use this feature to copy more language and proficiency than you can copy with this feature.