Opiates are literally everywhere, even in affluent areas (Chester County's main line area has issues, but they look different since they have money). Blight (assuming this is houses that don't look great) is going to occur anywhere there's a lack of money. The reason jobs don't fully fix the blight is that many of those people are on a fixed income and retired (elderly are an outsized portion of the population since the kids had to move away for work). The people who do have jobs tend to have well kept properties. I'm not sure about the pollution problem aside from some sulfur creeks in the region.

I'm sure there are plenty of candidate cities throughout the overall region, and it would likely depend on what the industry is. Someplace around Indiana PA would be good if you need semi close access to a commercial airport, a larger city, or a college. Erie could be similar. Johnstown PA area is good if you have government contracts, defense work, or need a regional or shipping airport. Bedford or Breezewood PA can be good for warehouses and shipping with the highways. Medium to small companies would be well served to position themselves between two medium/small towns for cheap land and larger workforce pool without being near the larger cities, like Millville and Stillwater as an example.