In Deathbringer, should DEF be based on DEX? (Patreon)

So I had the idea to base DEF (AC) on DEX. This makes logical sense: as the character rises in level their DEX and ability to DODGE blows improves. Now you can have a Conan type who fights without a shirt. 

This change would necessitate these changes to the rules: 

1) Armor would absorb damage instead of raising AC/DEF

2) The rules would have to cap all stats at 18, because a 20 AC/DEF is ridiculous.

What are your thoughts?