I think the difficult part with harnessing lighting is the consistency of it. We would need to build in places where thunderstorms are common, which will only be true for particular seasons. The other limitation is the battery technology that we currently have. It could be a better resource if we could find a way to store electricity in a non-degrading system. I think the new solid state batteries are supposed to be that way, but I don't know enough about them or this topic to really say. Alternatively, we can just pump people full of radiation until one of them becomes a weather controlling mutant so we can have infinite thunder storms.