I agree with Darwoth, percentage based combat would make combat character grind meaningless - thus nullifying efforts of most people.
Success in PVP should be reliant solely on effort and skill:
- Biles: effort of biling and developing up characters.
- Gear: effort of grinding T&N and harvesting cotton fields, or silver to craft/purchase high end gear and artifices.
- And naturally combat experience: being cunning and more experienced in combat should make a difference between opponents.
To be honest if someone has tried to change weapons in the middle of battle it's not the easiest task to do, since the pace of the combat is always fairly fast, and if it's a life/death situation that makes it even more risky to do. I don't think that should be penalized, people should be able to switch weapons because it just isn't that easy. (or I need to practice more..)