This system is meant to change the way that Armor Class is determined to become more flexible and grow with the characters. In the current system a character at level 1 with Breastplate and a shield with 14 Dexterity would have 18 AC, and they would keep that AC from level 1 to level 20, with no changes.
Bounded accuracy is a good system, and helps to keep things in line and prevent ridiculous extremes where a character can get such a high AC above others that it’s difficult to impossible to deal with. Yet if we look at that character with 18 AC at level 1 and 20, you will see that an Orc attacking them at level 1 has a 40% chance to hit them (+5 to hit). Yet once they get to level 20 and start fighting something like Cloud Giants the creatures will have a 85% chance to successfully hit them (+14 to hit), and the orcs accuracy remains the same. You have no feeling of progression, you feel stagnated on your defenses since level 1.
MAKING USE OF PROFICIENCY
Fortunately there is a way to change armor in a way that there is a sense of growth while maintaining a reasonable bounded accuracy, and that’s making use of a character’s proficiency bonus. This will cause a character’s AC to increase as they level, adding a sense of progression and advancement. Naturally just adding Proficiency to AC will cause extreme AC bonuses, our character would have 20 AC at level 1 and 24 AC at level 20, definitely a bit more extreme than desired.
What we would do is reduce the Armor Class provided from light & medium armor by 4 and heavy armor by 3. Then we would reduce a character wearing no armor to have an AC of 6 + Proficiency bonus + Dexterity modifier. Lastly, we give light armor a maximum Dexterity bonus of 4.
What this would do is cause characters at lower levels to be bit below the normal curve. If we took our Breastplate and shield user, their AC would be 16 at level 1, and it would improve to 17 at level 5. Once the character reaches level 9 this balances out to where it is in the normal system, as 18. Yet it grows stronger from here. At level 13 it becomes 19, and at level 17 the character caps out at an AC of 20.
One of the main objectives of this change is to provide a change that makes Strength a combat stat with different options in combat and a different play style than dexterity. In the core system, Dexterity is only around 1 point (5%) lower than Strength is defense, while offering generally better bonuses in the way of Ranged options, Initiative, a primary saving throw, and multiple skill rolls. Strength isn’t useless, but even in defensive builds it does not seem like a very good option when you look at what tools are available. This is why heavy armor suffers a smaller penalty to begin with, and we included a dexterity bonus maximum for light armor. This makes strength a better defensive option if available, whereas dexterity has much better versatility, a stronger saving throw, and a faster initiative.
NEW ARMOR TABLE
The below table can be used this this new system as a quick reference.
|Padded||7||+ 4||Disadvantaged||–||10 lbs||5 gp|
|Leather||7||+ 4||–||7||10 lbs||10 gp|
|Studded Leather||8||+ 4||–||9||13 lbs||45 gp|
|Hide||8||+ 2||–||–||12 lbs||10 gp|
|Chain Shirt||9||+ 2||Disadvantaged||–||20 lbs||50 gp|
|Scale Mail||10||+ 2||Disadvantaged||9||45 lbs||50 gp|
|Breastplate||10||+ 2||–||11||20 lbs||400 gp|
|Half Plate||11||+ 2||Disadvantaged||13||40 lbs||750 gp|
|Ring Mail||12||0||Disadvantaged||–||40 lbs||30 gp|
|Chain Mail||13||0||Disadvantaged||13||55 lbs||75 gp|
|Splint||14||0||Disadvantaged||15||60 lbs||200 gp|
|Plate||15||0||Disadvantaged||17||65 lbs||1500 gp|