[PF] Replacing Armor Bonus with Dodge Bonus?

[Sriseru]

I'm working on a Pathfinder campaign setting set in the bronze age, in a time before armor.
So I came up with the idea of making a new archetype for each class (except for paladins) which removes all armor proficiencies and in place grants a dodge bonus through level progression. I drew inspiration from the gunslinger's Nimble ability.
The maximum of this dodge bonus is equal to the highest armor bonus the various classes can "legally" possess (excluding enhancement bonuses).

I could really use some input on how to balance this dodge bonus, if anyone would care to give it.

Here are the archetypes:

Unarmored Barbarian (Barbarian Archetype)
Weapon and Armor Proficiency: An unarmored barbarian is proficient with all simple and martial weapons and with shields (except tower shields), but have no armor proficiency. This replaces the normal weapon and armor proficiency of barbarians.
Nimbleness (Ex): Starting at 1st level, an unarmored barbarian gains a +2 dodge bonus to AC while wearing no armor. Anything that causes the unarmored barbarian to lose her Dexterity bonus to AC also causes the unarmored barbarian to lose this dodge bonus. This bonus increases by +1 at 2nd level and then for every five levels beyond 2nd level (to a maximum of +6 at 20th level). This replaces armor proficiency with light and medium armor.

Unarmored Barbarian
Level Special
1st Nimble +2
2nd Nimble +3
3rd
4th
5th
6th
7th Nimble +4
8th
9th
10th
11th
12th Nimble +5
13th
14th
15th
16th
17th Nimble +6
18th
19th
20th

Unarmored Bard (Bard Archetype)
Weapon and Armor Proficiency: An unarmored bard is proficient with all simple weapons, plus the longsword, rapier, sap, short sword, shortbow, and whip. Bards are also proficient with shields (except tower shields), but have no armor proficiency. This replaces the normal weapon and armor proficiency of bards.
Lesser Nimbleness (Ex): Starting at 1st level, an unarmored bard gains a +2 dodge bonus to AC while wearing no armor. Anything that causes the unarmored bard to lose her Dexterity bonus to AC also causes the unarmored bard to lose this dodge bonus. This bonus increases by +1 at 8th level and then at 16th level (for a total of a +4 dodge bonus). This replaces armor proficiency with light armor.

Unarmored Bard
Level Special
1st Nimble +2
2nd
3rd
4th
5th
6th
7th
8th Nimble +3
9th
10th
11th
12th
13th
14th
15th
16th Nimble +4
17th
18th
19th
20th

Unarmored Cleric (Cleric Archetype)
Weapon and Armor Proficiency: An unarmored cleric is proficient with all simple weapons and with shields (except tower shields). Clerics are also proficient with the favored weapon of their deity. Unarmored clerics have no armor proficiency. This replaces the normal weapon and armor proficiency of clerics.
Nimbleness (Ex): Starting at 1st level, an unarmored cleric gains a +2 dodge bonus to AC while wearing no armor. Anything that causes the unarmored cleric to lose her Dexterity bonus to AC also causes the unarmored cleric to lose this dodge bonus. This bonus increases by +1 at 2nd level and then for every five levels beyond 2nd level (to a maximum of +6 at 20th level). This replaces armor proficiency with light and medium armor.

Unarmored Cleric
Level Special
1st Nimble +2
2nd Nimble +3
3rd
4th
5th
6th
7th Nimble +4
8th
9th
10th
11th
12th Nimble +5
13th
14th
15th
16th
17th Nimble +6
18th
19th
20th

Unarmored Druid (Druid Archetype)
Weapon and Armor Proficiency: An unarmored druid is proficient with the following weapons: club, dagger, dart, quarterstaff, scimitar, scythe, sickle, shortspear, sling, and spear. They are also proficient with all natural attacks (claw, bite, and so forth) of any form they assume with wild shape.
Druids are proficient with shields (except tower shields) but are prohibited from carrying shields made out of metal. Druids have no armor proficiency. This replaces the normal weapon and armor proficiency of druids.
Druid Nimbleness (Ex): Starting at 1st level, an unarmored druid gains a +2 dodge bonus to AC while wearing no armor. Anything that causes the unarmored druid to lose her Dexterity bonus to AC also causes the unarmored druid to lose this dodge bonus. This bonus increases by +1 at 2nd level and then at 7th level (for a total of a +4 dodge bonus). This replaces armor proficiency with light armor.

Unarmored Druid
Level Special
1st Nimble +2
2nd Nimble +3
3rd
4th
5th
6th
7th Nimble +4
8th
9th
10th
11th
12th
13th
14th
15th
16th
17th
18th
19th
20th

Unarmored Fighter (Fighter Archetype)
Weapon and Armor Proficiency: An unarmored fighter is proficient with all simple and martial weapons and with shields (including tower shields), but have no armor proficiency. This replaces the normal weapon and armor proficiency of fighters.
Greater Nimbleness (Ex): Starting at 1st level, an unarmored fighter gains a +4 dodge bonus to AC while wearing no armor. Anything that causes the unarmored fighter to lose her Dexterity bonus to AC also causes the unarmored fighter to lose this dodge bonus. This bonus increases by +1 at 2nd level and then for every four levels beyond 2nd level (to a maximum of +9 at 20th level). This replaces armor proficiency with light, medium, and heavy armor.

Unarmored Fighter
Level Special
1st Nimble +4
2nd Nimble +5
3rd
4th
5th
6th Nimble +6
7th
8th
9th
10th Nimble +7
11th
12th
13th
14th Nimble +8
15th
16th
17th
18th Nimble +9
19th
20th

Unarmored Ranger (Ranger Archetype)
Weapon and Armor Proficiency: An unarmored ranger is proficient with all simple and martial weapons and with shields (except tower shields), but they have no armor proficiency. This replaces the normal weapon and armor proficiency of rangers.
Nimbleness (Ex): Starting at 1st level, an unarmored ranger gains a +2 dodge bonus to AC while wearing no armor. Anything that causes the unarmored ranger to lose her Dexterity bonus to AC also causes the unarmored ranger to lose this dodge bonus. This bonus increases by +1 at 2nd level and then for every five levels beyond 2nd level (to a maximum of +6 at 20th level). This replaces armor proficiency with light and medium armor.

Unarmored Ranger
Level Special
1st Nimble +2
2nd Nimble +3
3rd
4th
5th
6th
7th Nimble +4
8th
9th
10th
11th
12th Nimble +5
13th
14th
15th
16th
17th Nimble +6
18th
19th
20th

Unarmored Rogue (Rogue Archetype)
Weapon and Armor Proficiency: An unarmored rogue is proficient with all simple weapons, plus the hand crossbow, rapier, sap, shortbow, and short sword. They have no armor or shield proficiency. This replaces the normal weapon and armor proficiency of rogues.
Lesser Nimbleness (Ex): Starting at 1st level, an unarmored rogue gains a +2 dodge bonus to AC while wearing no armor. Anything that causes the unarmored rogue to lose her Dexterity bonus to AC also causes the unarmored rogue to lose this dodge bonus. This bonus increases by +1 at 8th level and then at 16th level (for a total of a +4 dodge bonus). This replaces armor proficiency with light armor.

Unarmored Rogue
Level Special
1st Nimble +2
2nd
3rd
4th
5th
6th
7th
8th Nimble +3
9th
10th
11th
12th
13th
14th
15th
16th Nimble +4
17th
18th
19th
20th

[lesser_minion]

It's not a bad idea, although Unearthed Arcana foresaw this problem and came up with its own solution (http://www.d20srd.org/srd/variant/adventuring/defenseBonus.htm).

Also, I'm not sure you really want to name your class features in a way that suggests that the fighter is more nimble than the rogue.

[Sriseru]

I forgot to mention that I was using Pathfinder... Sorry about that.
Do you think Unearthed Arcana's Defense Bonus variant rule would be applicable to Pathfinder, or would it need some tweaking first?

[bobthe6th]

The UA rules are what D20 modern uses, so I think they are generally applicable.

Also... your armor bonuses are really low. Use the defense bonus system.

[Sriseru]

Yeah, I've been looking over UA's Defense Bonus rules over the past few hours, and I think I'll adopt them for my setting.
Thanks for pointing me in the right direction, you really helped me out. :D

[ericgrau]

The effects of armor's max dex bonus to AC are something to consider. If that's uncapped it could muck things up. Grab weapon finesse on a fighter and bam no attack roll can even come close to hitting you including touch attacks.