D&D 5E Proficiency bonus based AC and armor as temp HP with reduced AC bonus?

[Kobold Avenger]

The main idea is having a character's Proficiency bonus contribute more to their AC in a campaign where armor option are limited, restricted mostly to light and medium armor. Many characters therefore are going to be unarmored and armor's contribution to their AC is going to be reduced.

When it comes down to classes I see Fighters, Monks, Paladins and some Clerics having high AC based on class and proficiency bonuses, Barbarians, Clerics, Druids, Rangers and possibly Rogues being on the medium tier and every other class being on the lower tier unless they belong to a melee-combat focused subclass. With the 3 tiers in mind how would their proficiency bonus and Dex (or other ability score) bonus interact?

And though I said that armor was limited, it's not non-existent as it's for settings that are either less or more technologically advanced then the typically D&D campaign, breastplate is likely the best armour one could get for armour without getting a feat or belonging to a special subclass. I feel that if armour contributes to AC it's based score should be reduced because of the proficiency bonus. And wearing armor adds temporary hit points to the character, though it may be ruled that it's a special type of temp HP such as Armor HP. I only see the temp HP being in increments of 5, with heavier armors offering more temp HP. I've toyed with the idea that some armors might have a hardness or damage reduction. The temp HP of armor refreshes with a short rest, or a 1 minute Int check (proficiency armorer's kit).

There's also the possibility that some attacks might have the Armor-piercing quality, which might either bypass or do double damage to the temp HP.

 

[Flamestrike]

You could run armour as DR instead. Much less fiddly than Temp HP.

Light 2/-, Medium 3/- and Heavy 4/-. Or something like that.

If you really wanted to get fiddly, you could have Chain Mail provide an extra +1 vs Slashing (but -1 vs Bludgeoning) and so forth with different armours.

Then include the following rule:

''If your attack does not already have disadvantage from another source, you may make your attack roll at disadvantage. If the attack hits, you may ignore the DR granted by armour. ''

That simulates going for weak spots like visors and gaps in the armour etc.

 

[Tales and Chronicles]

I'd let everybody just be 8+prof+dex, unless you have another AC calculation (races, barb, monk etc). That's your ''to-hit'' number.
Shields still give +2 to AC.

Armors give special THP called Armor Points, they go first, then THP, then HP.

Light: 9 AP, no max dex.
Medium: 13 AP, max dex 2
Heavy: 21 AP, resistance to non-magical Slashing, disadvantage on Stealth and no dex to AC.

Restoring AP requires 30 minutes, with a check of 10+ the number of point you want to restore with a Int check made with Smith or Leather maker kit. You restore 1 AP per 1 over a result of 10 on the roll.

 

[jmartkdr2]

If you're going this route and want to keep it simple:

Make the base calculation for wearing armor you're proficient with 8 + prof + dex. This just flows with the rest of the rules better. However I would let characters proficient with heavy armor use either strength or constitution instead of dex so that you don't make dex even more of a 'must have' for all characters. If even paladins need a 14 dex, you'll only see rapiers and whips as melee weapons.

For the actual benefit of specific armors: I would just add to the character's base hit points rather than add a new category of hp. The amount could vary based on the cost of the armor (including how magical it is), ranging from +5 to +50 for epic-tier stuff. It'd be a lot of math to ensure balance with the existing numbers, but playtesting should get you there pretty quick if your players are willing to run a few scenarios.

You'd still want to work out how things like the defense fighting style and various armor feats work (or replace them with new options), but those shouldn't be too tricky. (the only one I foresee an issue with is Medium Armor Master, but that's a crappy feat already.)

 

[Kobold Avenger]

I'm guessing some consideration needs to apply to Mage Armor and the Mending spell.

In many ways Mage Armor is just Light Armor, so it could work that way.

 

[Dragongrief]

Maybe, maybe not for mage armor.

Depending how far you want to go with it, there are two main things that factor in: avoidance (current AC) and resistance/resilience (HP).

If something is mainly there to be a buffer when you get hit (most armors), then it's main benefit should be to resilience. To make sure it stays relevant, any bonuses should scale with level or proficiency.

If its effect is primarily to keep the attack away from you (shields, magic rings/cloaks), then it would apply to AC.

 

[Quartz]

Something with which I've toyed is allowing Fighters to use their Proficiency Bonus instead of Dex for AC, and possibly for Initiative later. This is in line with 'Hollywood Heroics' where the protagonists are usually lightly armoured. A PC can still have a max AC of 21 (Studded leather, shield, +6 PB, +1 Defensive style) without magic. But PCs can still don plate armour if necessary (for instance on a large battlefield, a PC might be denied her Dex / PB bonus and thus lose a lot of AC otherwise). I would extend this to allowing Palading to use similarly their Cha bonus instead of their Dex bonus.

 

[jgsugden]

An easier approach - at character creation you may elect to give up armor proficiency in exchange for a flat AC bonus when not wearing any armor. If you give up light, +2 (add dex) , if you give up medium, +5 (+ up to 2 from dex), and if you give up heavy, +7 (no dex allowed). If you give up heavy, you retain medium and light armor proficiencies. If you give up medium, you retain light.

 

[jmartkdr2]

Something with which I've toyed is allowing Fighters to use their Proficiency Bonus instead of Dex for AC, and possibly for Initiative later. This is in line with 'Hollywood Heroics' where the protagonists are usually lightly armoured. A PC can still have a max AC of 21 (Studded leather, shield, +6 PB, +1 Defensive style) without magic. But PCs can still don plate armour if necessary (for instance on a large battlefield, a PC might be denied her Dex / PB bonus and thus lose a lot of AC otherwise). I would extend this to allowing Palading to use similarly their Cha bonus instead of their Dex bonus.

That's an interesting idea, although it makes a Hexblade dip even sweeter for the paladin.

 

[DND_Reborn]

Something with which I've toyed is allowing Fighters to use their Proficiency Bonus instead of Dex for AC, and possibly for Initiative later. This is in line with 'Hollywood Heroics' where the protagonists are usually lightly armoured. A PC can still have a max AC of 21 (Studded leather, shield, +6 PB, +1 Defensive style) without magic. But PCs can still don plate armour if necessary (for instance on a large battlefield, a PC might be denied her Dex / PB bonus and thus lose a lot of AC otherwise). I would extend this to allowing Palading to use similarly their Cha bonus instead of their Dex bonus.

It is an nice thought but IME light armored PCs typically have good (16) to great (20) DEX anyway.

It does help make DEX less of a "god-stat" though, which is always a good thing.

Sigh, time to mull over another house-rule...