[Kit concept] Lightning mage

This is less a complete champion idea than some synergistic ability ideas.

Passive: Charged Target - Champions hit by abilities become charged with electric energy for 3 seconds. When this ends, it discharges for damage to the nearest target. Charges stack.

Ability: Forked Current - Hits target, then forks to two more targets in the same direction for 80% damage each. Each of these forks for 60% base damage. The secondary forks can go to one target, for 120% the initial hit damage. Bounce is mechanically like Double Up. Checks for Charged Target instead of Impure Shots.

Ability: Ionized Column - Charges an area with energy. After 1.5 seconds, deals damage to all enemies in the area. Each additional target reduces damage by 15%, to a minimum of 40%. Plays off passive - isolated targets get hurt hard. Sort of like Karthus Q, but I'm thinking a region like Cho'gath's Rupture area.

Ability: Return Strike - Arc of lightning from target spot towards champion. Curves to track. Skillshot. Penetrates enemies. Basically, the return half of Ahri/Sivir Q from a target location.

Ultimate: Overcharge - Target enemy takes damage, then constant damage occurs to any OTHER enemies nearby. Ideally, isolates a target, allowing comboing with Column.