How about the same idea in another game?
When you hit hard, you hit hard! Gain the following advantages:
- Increase one ability score by 1, to a maximum of 20. You MUST be able to make an attack that uses this ability score
- When you score a critical hit, either through a spell or a weapon attack, you may make another attack as a free action. This attack can be a weapon attack or a cantrip that uses a spell attack roll.