No, they can't achieve control that way.

1. It's not possible to accumulate a significant proportion of the current supply without pushing the price up commensurately. And as is pointed out in the OP, the legitimacy is also pushed up. Incentive to sell back to fiat is further lessened.
2. Not all supply currently exists, so this could never be a one-off, it would have to be a permanent reserve purchasing policy, as otherwise their previous position gets eroded by the newly mined supply.

Fascinating read, thanks. I speculate that the chance of this author being noticed by IMF heavyweights is slim to none because of his place in the global financial pecking order. Whether that is good or bad (or true) I can't tell.

http://www.polisci.uci.edu/node/1308

Ah very interesting.  Too bad, he's still in law school, but still, being the first to publish a paper on this particular topic, it sets a precedent, and perhaps it will get noticed and forwarded and looked at in higher circles, or maybe the IMF will use him as a consultant.  Given our current Bitcoin-as-buzzword environment, maybe some news outlets will also pick it up and it can get some mindshare that way as well.

This ... BitCoin is not a single company, there is no "The Bitcoin Company" running the bitcoin servers, or even a single decentralised network. It is open source for creating monies ad infinitum, i.e. armageddon for anybody still harbouring illusions of monopoly power over monetary issuance.

The dollar is not the world’s first reserve currency and it almost certainly will not be the last. The same status has been achieved by an abundance of currencies over the last 2,500 years as their issuing nations gained and lost economic prominence. Accordingly, the fate of the global financial system is tied to the success or failure of individual nations and, as the chart below illustrates, the USD is approaching the average lifespan for this role.
Historical Reserve Currencies

The sentiment that the time has come for an alternative seems to be underlying the actions of financial decision makers internationally. The share of global reserves held in USD has fallen approximately 10% so far in the 21st century and calls for a replacement for the USD have been posed in recent years. China has repeatedly suggested removing the USD from reserve currency status, as has the International Monetary Fund.

One of the most popular alternatives discussed on the global stage is the IMF’s Special Drawing Rights (SDRs) – claims on a basket of currencies, the composition of which is determined by the IMF Executive Board. Given the propensity for intentional manipulation of important financial benchmarks and increasing contention caused by international monetary unions, the prospect of going further down path of consolidated power with the SDR is disconcerting. As would be expected, some countries are beginning to show visible angst towards the global fiat system in general and have begun repatriating large amounts of physical gold.

In a world of increasing global communication and trade, a nation-agnostic currency would solve many of the problems we’ve seen repeated throughout history and potentially ease the associated international tensions. An asset for which the value is determined solely by international demand, immune to influence from central planners, is a necessary step forward towards a free market.

Only recently have the technologies required to facilitate such an idea existed, so for the first time in history, the next shift in reserve currency could be to one not controlled by government(s) or banks. Bitcoin may not be the solution, but categorically speaking, there’s a strong argument that it’s a step in the right direction.