Well there would be an increased risk of bitcoin collapsing if that should happen. The question is, what would they gain from it, aside from taking down a yuan competitor? If they bought cheap bit coins, those could become even more useless when a news of a mine takeover gets out. I think it would be more likely for them to keep a thumb on the miners, like how they do to other private enterprises.
A government declares something illegal, takes over the "illegal" business.. only to continue running it.
Lacks principle. Big Hypocrisy and very immoral
Governments are not exactly known for strictly adhering to moral principles.