Yes: they would immediately have the entirety of their currency reserves existing outside their economy. This would necessitate buying their entire money supply from neckbeard speculators and drug dealers, which would provide an interesting challenge. Furthermore, the buy pressure would enrich said neckbeard speculators at your country's expense, and they'd probably post some positive things about you on Reddit for a few weeks. What great PR!
Additionally, they would have zero control over their fiscal policy. They would be unable to adjust the money supply to meet economic conditions. Rather, money supply would be set by Chinese mining conglomerates and whether a handful of whales feel like buying or selling on any given day. This would remove a major headache of governance: why worry about what you can't control?
Furthermore, it would require the entire economy to become 100% digitized. No cash deals: not for a newspaper on the sidewalk or a can of Coke at the corner shop. Imagine the benefits that linking every vending machine, newsstand, and POS to the Internet would have! (Do not bother imagining the costs.) Imagine the economic stimulus caused by forcing every citizen to have a smartphone or starve! Imagine the excitement and adventure a power outage would create! Imagine your country's burgeoning security industry in an arms race against Russian hackers! Don't fall behind or your country loses everything--haha, what fun!
Also Bitcoin is 100% anonymous and will end taxation and destroy the State. As a head of state, I am sure this argument will appeal to you.
But also the opposite is true! Every citizen's entire economic life would be 100% transparent and trackable! Nothing could hide from the watchful eyes of your revenue service. (Also, imagine knowing everything your political opponents buy, and where they buy it! Useful, eh?)
Bitcoin will make banks superfluous and useless. Your banking and financial services industries are just parasites. Let them leave. When have banks ever assisted in economic development and growth? Never. That's probably the answer to that question. I would guess never.
Also there are no charge-backs. I'm sure that would help something. Fuck charge-backs, man.
Finally, the 2.7 transactions per second limit would help your economy take a more leisurely pace. Imagine all your citizens sharing that limit together! (Also sharing it with miners, Chinese day traders, and dice gamblers). No need to hurry hurry hurry everywhere! Life is too fast paced. Why not order a coffee, then sit around waiting a few hours for confirmation? Slow life down a bit.
Really there's no downsides imaginable.