How I would have done Ao Shin's kit.
Passive: "storms of fortune" ao shin generates flow (same formula as Yasuo) with his movement which is used as a resource, which give him a small tenacity bonus based on the percentage the flow bar is filled. Every time he uses an ability, ao shin consumes some of the flow he's built up, but upon use, gets a shield (on a medium cooldown unaffected by CDR) and some bonus % movement speed for a duration based on his own movement speed and other factors of his abilities. The remaining time on a speed boost does not carry over to the next cast: if you cast a short boost partway through a long boost, the rest of the long boost will be canceled.
Q: "lightning strike" ao shin consumes 1/12th of his max flow, giving the longest passive speed duration of his kit. His next auto attack deals bonus magic damage in an area and causes the speed boost to reduce the remaining time by half. The cooldown is relatively short 45% CDR putting it at maybe 5 seconds.
W: "rain's pardon" ao shin consumes 1/6th max flow to either tether to an ally (100% benefits or himself(giving 75% benefits), giving a short speed boost to both(shorter to just him) that ends with a heal based on ap. Has a medium cooldown 45cdr@ maybe 8 seconds
E: "thunderous winds" ao shin consumes flow –based on how long he charges up– up to 1/3rd of his max flow in increments of 1/12th his maximum flow. Upon cast, he charges in a direction, pushing the first enemy champion hit 1/2 the distance remaining on the channel dealing magic damage based on ap, the distance the enemy champ is to be pushed and gives ao movespeed based on the distance ao travels. Relatively long cooldown 45cdr@13 seconds. Rate of charge 1/12th every second unaffected by CDR. Cannot pass through walls. conditionals: if collides with wall alone, is slowed (debuff: staggering winds) instead of getting ms boost, collides with enemy, deals none or a flat bonus damage (requires balancing) but transfers slow and gets full ms boost. can be charged and cast while moving for a movement speed reduction during the channel.
Ult: "dragon's storm" disengage/engage tool where during a channel only interrupted by displacement/knock up, consuming 50% of his current flow or something he surges in a target direction for a distance (based on % max flow used for the cast) leaving behind a wide(2/3/4x rumble ult width) storm trail that surges opposite the direction he travels and lingers for a few seconds. for values based on his passive's ms components, Enemies traveling against the storm winds are slowed up to 4 times the slow applied by allies, allies traveling in the direction of the storm winds travel up to 4 times faster than enemies. If he hits 1 enemy, he knocks them up for small damage and goes through for half the remaining distance, if he hits a third, they are knocked back for small damage and his travel is stopped. Additional stats include tenacity bonus max [rank 0: 5%] to 9%/13%/18% his ult Does not give him passive ms as ms/slow is in the storm in a certain direction
I don't know what I'd do with base stats but I'd probably make him lightly tanky early, with subpar tank scaling in magic resist and armor, mediocre-subpar hp regen, reasonable health scaling, relatively slow movespeed somewhere between 330-340 range, reasonable ad and as that doesn't scale well, and ap that does scales well.
I'll be the first to say this idea is a little overloaded, but the synergy and decision making for your abilities is what I focused on.