Way of Speed

All credit goes to Matthew Cmiel, the youtuber/patreon owner/dungeon master who originally came up with this subclass. 

Inspired by speedsters such as Quicksilver, the Flash, and Sonic the Hedgehog, the Way of Speed revolves around the monk using its ki to weaponize its speed, involving needing to pay attention to distances on the battlemap for the purpose of getting the most out of basic attacks using Blinding Speed, along with giving the monk abilities to deal with multiple enemies at higher levels. 

Blinding Speed

At 3rd level, you gain the ability to use your speed to improve your damage. When you spend movement to enter into melee range with an opponent, you may spend 1 ki point to add additional damage to the attack. The rate is 1 martial arts die per 10 feet of movement in a straight line. (so if you move 20 feet, you add 2 martial arts dice of damage). You may only add this bonus damage once per turn.

The bonus damage from Blinding Speed is also capped to base walk speed as affected by the base 30, unarmored movement, and feats like Mobile. Walking speed increases from magic items like boots of speed, racial features like Feline Agility, or from spells like haste don't count.

Ready to go!

You have trained your body diligently to react to any stimuli incredibly quickly. This breathtaking speed gives you advantage on Initiative rolls.

Quick Reflexes

At 6th level, your reflexes permit you to move so blindingly fast that you become incredibly difficult to hit. Spend 1 ki point to impose disadvantage on an attack roll. You can spend this ki point after the attack is rolled.

I Know Where To Step!

At 6th level, you learn how to move across all sorts of terrain without incurring penalties. You can step over the problems, make continuous jumps, or whatever seems appropriate to move through difficult terrain with no penalty.

One with the Speed

Your control over your body grants you the ability to create certain effects that function like spells.  Your spell attack modifier is proficiency + Wisdom. You spell saving throw is 8+proficiency+wisdom. You gain the following spells that you can cast with the following ki expenses, and at the following levels. 

Available at level 11

Gust - 1 ki point
Gust of Wind - 2 ki points
Warding Wind - 3 ki points
Fly - 4 ki points
Wind Wall - 5 ki points

Available at level 17

Investiture of Wind - 6 points
Whirlwind - 7 ki points

Lightning Speed

Your Blinding Speed ability may now be used multiple times in a turn, with the same movement added for each attack. For example, if you charge 60 feet in a straight line towards an enemy, you can then spend a ki point to do an additional 6d10 damage (martial arts die), and may spend an additional ki point to do it again for your second attack.