Sona: Song of Celerity

Song of Celerity: Make its effect on the enemy champion an AoE slow instead of being transferred to her passive Power Chord-Tempo

Disadvantage: being a squishy, I think that would balance the change to AoE slow effect. She can go in the middle, instead of being way at the back, of the team fight. And any good player will shift their target to squishy ones, like her, before going after those tanky ones.

Advantage: An AoE slow effect to enemy champions