So, I think Max Dex doesn't work. Most here aren't keen on a Dex Penalty. What about removing any dex cap altogether, only have one armor per category, and overall improving medium and heavy armors and shields. Arcane spell failure is also removed in place of having Armor check now effect Concentration. A push towards simplicity.
When fighting defensively or using the full defense action, the base shield bonus to AC doubles. Base here just means the enhancement of an magic shield doesn't double, so a +2 Heavy shield goes from granting a +5 AC up to a +8 (not a +10). Anyway, here's the stuff I've been working on.
Improved Shields
While Bucklers still grant the normal +1 Shield AC and Tower Shields grant the normal +4 Shield AC, Light Shields now grant a +2 AC bonus and Heavy Shields now grant a +3 AC bonus. Bucklers, however, will no longer grant the -1 penalty to hit for off-hand attacks. Tower Shields now have no max dexterity restriction. Using that shield-hand to perform an action or attacking with the shield still negates the shield bonus to AC for that round.
Improved Buckler Defence and Improved Shield Bash and other effects have been subsumed into the new feat: Improved Shield Use.
PROF______ACCESS
None.......... Basic armors, Basic bracers
Light........... Light armors, Buckler, Light Shield, Light bracers
Medium....... Medium armors, Heavy Shield, Medium bracers
Heavy......... Heavy armors, Tower Shield, Heavy bracers
I really like the idea that there is mechanically only light, heavy, etc armor and thematically it is considered Chain shirt, fullplate, whatever. No max dex, no arcane spell failure, but stiffer armor check. Buffing up medium and heavy armor means it should be rarer, so now only Fighters and Paladins get it automatically and Clerics only get medium armor prof.
ARMOR_________________________ARMOR CHECK___PROF
+1 Basic (ex: Clothing) ..........................-0.............none
+4 Light (ex: leather, chain shirt)..............-4.............light
+7 Medium (ex: breastplate, bandedmail)...-8...........medium
+10 Heavy (ex: fullplate, splintmail)..........-12...........heavy
SHIELD_______HAND USE_____ ATTACKING W/ SHIELD__ PENALTIES
+1 Buckler .......any item, any wpn..cannot attack ............use > no +AC
+2 Light Shield ..any item, no wpn...as per Light weapon ....use > no +AC
+3 Heavy Shield .no item, no wpn ...as per One Hand wpn ..use > no +AC
+4 Tower Shield .no item, no wpn ....cannot attack ...........-2 to atks
New Feat: Improved Shield Use
Your have trained in using shield for offence and utility as well as defence.
Benefit:
Performing an action with your shield arm or using your shield to attack with does not remove the granted shield bonus to AC as normal. Using a Tower Shield does not incur a -2 penalty to attack rolls.
BRACER TYPE_______ARMOR CHECK___PROF REQUIRED
+1 Basic Bracers...................-0...........none
+2 Light Bracers...................-2...........light
+3 Medium Bracers...............-4...........medium
+4 Heavy Bracers.................-6...........heavy
Though Bracers do grant an armor bonus, if enchanted they can gain further enhancement bonuses or can gain shield enchantments but NOT armor enchantments (ie: so they cannot get enchantments like any of the Fortification, but they could get Arrow Deflecting or Reflection). Wearing Bracers does NOT count as wearing Light, Medium, or Heavy armor (just as it is currently).
I also included Defense bonuses (that do NOT stack with any armor bonuses) to my campaign. Because I'm big into level tiers and 5 level increments (like 4E), I changed the defense bonuses and the way weapon & armor enhancement grow to reflect that. Mechanically, you could just think of it as a free bonus regardless... great for when you have to take off your armor to sleep. Thematically, it well demonstrates an urban and civilized area where not everyone has to be tanked out in chainmail or fullplate to survive and promote more choice for mages and low-armor types.
DEFENSE BONUSES
CHAR LVL__NONE__LIGHT PROF___MEDIUM PROF___HEAVY PROF
1 ................+0............. +1............. +2................. +3
6 ................+1............. +2............. +3................. +4
11 ..............+2............. +3............. +4................. +5
16 ..............+3............. +4............. +5................. +6
21 ..............+4............. +5............. +6................. +7
26 ..............+5............. +6............. +7................. +8
31 ..............+6............. +7............. +8................. +9
36 ..............+7............. +8............. +9................. +10
Clear as mud?