One of Paducah's claims to fame is that is has one of the nation's largest storage sites for low level nuclear waste. It's not too far from a pretty substantial fault line too.
I like the thought of balancing the state by adding Paducah instead of Florence. Florence is within 20 miles of Cinci, and Covington & Newport are right across the river from Cinci. It would be fun to have it on a CC map, but I don't know if would be the best fit gameplay-wise.
You could also use Ashland or Hazard as options if you are looking to space out the cities a bit. Neither have very big populations, but Ashland has a pretty substantial oil refining industry and Hazard seems to have some strange notoriety within the state (I was raised in Northern Kentucky).