The state is both poor and utterly dependent on coal mining. The "escape hatch" does not have to be a set of exemptions, but new energy and/or mining options: wind turbines on mountain ridge crests, nuclear energy for Appalachia, high-tech, low-impact rare-earth mining for the electronics industry, deep-rock CO2 storage (if it's possible). I'm sure the underlying Marcellus Shale will be mined for natural gas, though I'd prefer that to be a stopgap measure only. The federal government could incentivize new businesses by offering tax breaks in exchange for well-paying jobs. There are probably many more other possibilities I've overlooked.
We are probably also going to have to deal with coal for some decades yet, though I do not like it. Even
http://www.greenpeace.org/international/press/reports/energy-revolution-a-sustainab">Greenpeace is willing to allow coal-fired energy generation for as long as the next 50 years. West Virginia, and other impacted areas, should be used to produce the last of the coal while transitioning to new technologies.
Our plans to change over to low-carbon energy will be able to happen much more quickly if some flexibility is built-in. Since the program is likely to be decades long and cost trillions of dollars, there will be many opportunities to "tweak" and "leverage" what we have at our disposal. And there's no time to begin like now.
--d!