I realized I don't think I asked the question as I wanted. In this scenario the country doesn't switch to the coin, the currency is just BTC, built upon BTC, and will continue to rely only on BTC, not some foreign currency like USD or Euro. What I'm thinking is just a new country. Like the idea of Esperanto land.
If as a new country and it to peg it currency to Bitcoin, then they should expect their economy to be a complete mess. Bitcoin is known for instability in price. Best idea is to accept it as one of payment means and not as general currency.