What if you set up several sock puppet mining pools, all supposedly independent and in competition with each other, and beat the existing pools on fees by enough that miners join you en masse? That would take some investment on your end as you would have to run pool infrastructure at a loss. But if you are a nation state, it's not a huge investment. You don't need to have any mining hardware of your own if you offer miners better returns for the use of their hardware than the other pools do.
Once your pools, taken together, have a dominant share of miners, I would think you could run a 51% attack without ever acquiring a single ASIC. The reputation of your pools will not survive but I think you could complete a 1 hour attack (reversing 6-conf transactions) before you lose the miners.
Would this work?
