Rolling for defense?

Hi everyone,

I like the idea that practically any action where the outcome is uncertain is handled with a roll, and when that roll is made against an opponent, the opponent needs to make a contesting roll. When a character attempts something requiring a feat of athleticism, such as lifting something heavy, they must roll a d20 and add their STR. When an attempt like that is made against an opponent, like trying to restrain them, both roll a d20 and add their STR. Pretty standard, nothing crazy.

However, I want to carry this system over into attack and defense rolls. The attacker rolls a d20 and adds the appropriate ability score, while the defender rolls a d20 and adds their defense score. This is similar to an optional rule in Knave 1e. Because I am hacking Knave 2e, I have item slots. A single piece of armor occupying an item slot (max of 7) counts as a point towards the character's defense score. If you want a more evasive character, each empty item slot up to half of their DEX score (so max of 5) is added to their defense score.

This means if you have 10 DEX and at least 2 CON, you could have a +12 defense score, but all of your slots would be occupied. I think this is balanced, partially because of the item slot system, because an attackers to hit bonus can be as high as a +10, and because the defender can still roll low and the attacker roll high.

Ultimately, I have a really hard time looking at things and seeing how it could work out. If there are any obvious problems please tell me, I'd love some feedback.