AD&D 2e: Simplified Modifiers

Before D&D 3rd edition there were no unified ability score modifier based on the base ability score. This was done to help make every single ability score value be important as it provides a benefit of some kind. However since the advent of 3rd edition it hasn't become that big of a deal to have odd value ability scores (especially if you're playing in a game with ability score damage).

So here's my take on a unified ability score modifier for AD&D 2e:

Value	Modifier
1	-4
2-3	-3
4-5	-2
6-7	-1
8-14	+0
15-16	+1
17-18	+2
19	+3

This takes the average of all modifiers for each ability score and then simply adds them together. Fans of AD&D 2e will note that there are no percentile bonus for Strength 18. Here's an optional rule to handle those in this system:

Optional Rule: Exceptional Strength
It can be quite difficult to gain a score of 18. Fighters, Rangers and Paladins who have an 18 or higher in either Strength or Constitution gain the following benefits.
Strength 18

You roll 1d20 on the following chart:

1- 11: You deal one and a half times strength modifier for weapon damage.
12-19: You deal double strength modifier damage for melee weapons.
20: You deal two and a half times strength modifier damage for melee weapons.

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This effectively results in the same final effect (with certain exceptions, such as bonus languages/proficiencies) without all of the various different modifiers to have to track.