Idea for Ryze

There's a bug where Ryze can charge up three runes: http://boards.na.leagueoflegends.com/en/c/bug-report/jGFHicni-gameplay-cosmetic-ryze-can-have-3-runes-loaded-displayed

This got me thinking. What if Ryze could charge up more runes for other effects. Just hear me out please.

The current passive is dull. It just gives more mana. My idea is that the passive is replaced. Instead, when 4 runes are consumed, ryze will have a very small amount of spell vamp and AoE damage. This is not a buff, but a change. Ryze will need to refrain from casting overload for four spells to gain the benefits. In exchange, the mana pool/damage will be lower without the free mana. It gives the player the option whether or not to charge up power, or go full dps.

Arcane Mastery INNATE: Ryze's maximum mana increases by 5% per 100 AP. Ryze's other basic abilities reset Overload's cooldown and generate a Rune for 4 seconds, up to a maximum of 4. If Ryze consumes 2 Runes, he shields himself from up to 60 - 200 (based on level) (+ 60% AP) (+ 3% bonus mana) damage for 2 seconds and gains bonus movement speed for the duration. If Ryze consumes 4 Runes, he gains 4 / 8% spell vamp and 6 / 12% AoE damage for 2 seconds.