How about the same idea in another game?

Press Advantage

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.

Thoughts?