Resident CCW permits should be valid in all 50 states. By creating reciprocity throughout the states you are allowing citizens who are traveling across the US the ability to protect themselves, their families, and those around them better without having to worry about becoming a felon by not knowing a particular state's law.
The easiest way to do this, in my mind, is to allow a CCW permit holder to abide by their state's CCW laws even when out of state. This way, the power is still up to the states, mostly, and, they only have to worry about knowing one set of rules.