Fiora Rework Idea:

Passive: Fiora will automatically block any auto attack directed at her (melee or ranged) if she has an auto attack available, and will expend the auto attack to make the riposte / deflect the attack. Neither the incoming attack nor the riposte will do damage.

Drawback: Fiora's auto attacks can be blocked by auto attacking her during her attack animation. Her damage output against any target can be diminished if anyone focuses on auto attacking her.

Unique characteristics: Fiora cannot lose a purely auto attack based duel if she can match the attack speed of the attacker. Fiora cannot win a purely auto attack based duel if the enemy can match her attack speed. Fiora cannot be harassed out of lane with ranged auto attacks. Fiora can miss minions if you block her attack by attacking her just before she begins to make the last hit.

So essentially the ability is a double edged sword. It has enormous strengths and weaknesses and helps to clearly define who she is. Her abilities would be replaced with new abilities, but they would only exist to reinforce her auto attack and passive.

Her Q would cause her attack or riposte to flourish through the target of the attack, and appear on the other side, and lasts 3 seconds.

Her W would cause her next riposte to trigger on any projectile spell and the cooldown is refreshed if the projectile is blocked. (mana cost can still be prohibitive and her spell block riposting ability can be overwhelmed with enough auto attacks because she won't have any ripostes left ) If her next riposte blocks an auto attack instead of an ability, the cooldown is not refreshed.

Her E would cause her next attack to function as if it were a melee physical damage spell and allow her to ignore bonus armor (but not innate armor). The attack can still be blocked using the rules of her passive. She can have a maximum of 3 charges stored.

Her new ult would allow her to riposte for free (doesn't consume an auto attack) for the next 5 seconds. There is no limit to the number of times she can riposte during this time.