You do it throughout the inflationary period of bitcoin. At which point bitcoin has replaced dollar, you as the govt own most of it, all the while you have also been cornering the block chain by ramping up govt controlled cpu power. You then set your miners to ignore zero fee / low fee, thus effectively enforcing a minimum price for transactions that have any need to go through quickly. Now you are taxing the world. Welcome to The New New Order!
I'd agree your plot is feasible, but as NewLiberty put it, the cat is out the bag.
I see Bitcoin as voluntary, you are not coerced into using it, (maybe you are if Fiat is collapsing - and that is part of your plan)
So given the voluntary nature, why not switch to a new crypto currency and avoid the monopolistic tax, or even carry on under a different fork? (problematic for obvious reasons and not inviting an answer to the forking idea)