Prototype system:

Strength

Speed

Dexterity

You start with three points to allocate, and you'll get one point after each arena win.  

When a character attempts to strike a blow we'll roll for both characters and add speed for the defending player, and dexterity for the offending player. Higher roll wins out. Then the defending player gets a saving roll based on armor level.  Higher Armor level gives you a higher chance to save when struck, but will give you a penalty to speed. 
After the blow is struck, strength determines the severity.