Running speed appears to be difficult/impossible to change in the way you describe (in fact we did have some ideas about it, but it turned out to be too hard to implement).
The suggestion itself has some merit imo, I would like to see something like it also. Though at the end of the day, it might not be very different from simply "finishing" a character - it's just another reward for accumulating a certain amount of karma, experience points or caps. In general, I think the longer it takes for a char to reach maximum potential, the more people will tend to stick to one or just a few chars. So that's good.
But if the rewards are too powerful, it might become hard or even impossible for lower level players to compete at all, which is something we want to avoid. You should be viable for combat even if you don't have the best stuff or the highest level. Otherwise we're promoting a situation where players tend to go only with min/maxed chars (which in itself leads to alting) and only tier 3 gear, which reduces the number of practically useful weapons and armors for everyone.