Disadvantages of your system: (half serious as well)
- new players with both Weapon Skill and Armor Skill at rank 0 have an undefined level rather than level 0
- levels are no integers, so there is no traditional joy when you get a level, because leveling is a more gradually process in your system
- the quality of the weapon and armor you use is not included. You may say that levels are only based on characteristics of the character, and not on his possessions, but I think such a difference is merely artificial. Your level should determine who's the most powerful fighter, better gear makes you a more powerful fighter just as much as better skills.
- your system is biased towards characters who balance their offensive and defensive skills. People who put all their efforts on their weapon skills and none on armor skills stick on level 0 in your system
