What we did for the community tortle (which will come out next update) was to catch the DEX modifier and subtract it when unarmored, if armored, we set any worn armor bonuses to 0. This leaves shields and magic bracers/rings alone as is indicated by the tortle. It's not beautiful, but it works. It also allows a tortle to wear armor of resistance and get the resistance granted, but not the AC.
Post-attributes/5000
Code:
~ If we're not shown, just get out now
doneif (tagis[Helper.Disable] <> 0)
var dexmod as number
dexmod = #attrmod[aDEX]
~ turn it into a penalty
dexmod *= -1
if (hero.tagis[Hero.EquipArmor] = 0) then
~ we are unarmored, remove Dex bonus by adding it's negative value back
hero.child[ArmorClass].field[tACUnarDef].value += dexmod
else
~ we are armored, strip all armor bonuses
hero.child[ArmorClass].field[tACDexMod].value = 0
foreach pick in hero from BaseArmor where "Helper.CurrArmor"
~ kill off any type of AC modifier
eachpick.field[arAC].value = 0
eachpick.field[arBonus].value = 0
eachpick.field[Bonus].value = 0
nexteach
endif