Gut his passive: Yasuo now builds flow by moving and attacking. He can only get to 80 flow by moving, the other 20 has to be earned by hitting things with his Q (he gains 5 flow per thing struck with his Q). As Yasuo's flow builds, he gets a movement and attack speed buff.
Q is now just the stab and the spin.
W can be cast at 100 flow, using up all of Yasuo's flow. Gives him a shield and a spell shield. The duration of the shield and the spell shield is based on his flow, and the magnitude of the shield is based on his flow. Yasuo can cast this at any time to give himself a shield and spell shield, but if he's below 50 flow he doesn't get the spellshield.
E is the same as it is now. Each dash costs Yasuo flow. If the dash kills its target, or if it dies by Yasuo's hand within a few seconds after dashing to it, the flow cost is refunded.
R folds the tornado and the anime into the same ability. At 100 flow, Yasuo can cast R to charge up a tornado in a manner akin to Xerath's Q. The damage the tornado does, how far it goes, how long the knockup is for, and the radius of it are all dependent on how long he charges it for. Yasuo can be interrupted during this. Once the tornado flies, Yasuo can recast his ult to do his anime shit to anyone that's been knocked up.