But he is a pretty good driver. He's not a gymnast and doesn't have Acrobatics but he certainly has Breakfall. Plus, making his DEX lower would only save a few points at the expense of buying Skill Levels with Driving and Breakfall. Going down that road seems very GURPy to me. I tried to balance the 'accuracy' of the build with the idea that his abilities have been upgraded and simplified over time. I purposely did not give him more than 2 Skill levels* of any one type with that in mind (he is best with a pistol). Especially the Overall ones since I consider having 3 of those in the realm of a minor super ability since that is the break point for doing tasks 1 step down the time chart.
* I made an exception with PSL's due their unique nature.
Also, I can see pure martial artists with a higher DEX and even Lightning Reflex bonus than John has but not with the gun skills as well.