In short, he isn’t so keen on the common approaches (maximum/double damage on a natural 20, or natural 20 plus confirmation roll). He suggests an alternative rule where if you roll five or more above the number you needed (in D&D 3.x, hit an Armor Class five points higher than the target’s) you can roll a d10 to determine the critical effect. Critical effects can include a bonus to your next attack on the target, a bonus to Armor Class against the target, or a free attack against the target.
[Or for the truly masochistic, I suppose you could break out the Rolemaster tables...]
Lately I’ve had a huge interest in ‘qualitative, not quantitative’ effects. I can get behind the idea of replacing ‘bonus damage’ on a critical hit with ‘special effect’ on a critical hit.
I’m not entirely happy with the implementation, though. Potentially three rolls for each attack seems a little much, and I’d like to have the option of ‘better qualitative effects’ for more-skilled fighters. This could be done with three rolls by having a modifier on the critical die (the d10), but… that’s getting even more complicated.
Long ago, in the before times (mid-90s, in other words) I considered a critical system where the bonus damage was based on the number rolled… but counting down. The lower the number on the die on a successful hit, the more damage you could expect to do. This also took some of the sting out of the natural 20 rule (automatic hit) rule commonly used because I ruled that if you needed that rule to hit the target, you did only half damage.