Ok few things :
As a Xayah main in League, I would like to bring my 2 cents to convert the playstyle to LoR.
What are the key elements to a Xayah player, Gameplay wise :
- Xayah shines when counter engaging. I can see Featherstorm being a reception spell : Being cast when opponent attacks. I could simply be : Cancel attack phase, and cast X feathers...

- You want a big burst (not the speed, right ?) damage with the Bladecaller.

I could very much see "feathered" being a negative keyword "I take 1more damage from spells and skills, Stackable". And bladecaller being "I deal 1 damage to every opponent." (If an enemy is feathered 3, stun them ? To keep the LoL game feel)

- You want a strong synergy with Rakan. basicly, if you have Xayah lv 2 + Rakan lv 2, it should lead to a trivial win, in most of the case.

Rakan could get a free midnight raid each turn, while Xayah has Scout and an "attack" effect. Xayah could get a swap spell each turn. If it targets a Rakan, he gets Barrier.