all the big early adopter will sell all their coins to you and start a new blockchain. everybody else will follow because they can get their money out safely and one very big holder is just to big a risk to your own investment.
read the op again
Still wouldn't work... Not much use in controlling the bottom price if the currency is adopted by a nation. The actual price of each BTC will rise so much that the 210 mil wall will be pitifully inadequate.
Incidentally, if I saw someone putting up a 210 mil wall, you'd have to pry the BTC out of my cold dead hands! You'd have to be an idiot to sell und those circumstances.