This isn't going to work the way you think it would work. Although the idea is non-evil, it will never happen.
If you create a "non free market" situation where a giant lump of cash is keeping the price fixed... Then you are giving hackers / theives a huge amount of money once they steal it. They can sell it all at once, and your "investors" or whoever put in the 21$million is the one going to lose a ton of money. Why would any investor agree to such a situation?
And even worse is if suddenly noone likes this block chain anymore, they can all cashout and your investors are stuck again with worthlessness instead of their $21million.
In fact it would make the most sense for everyone to just cash out and start a new block chain without the $21million blocker on it. Everyone wins except the guys who put up the $21 million.
Sure is fun to tell other people to put up a bunch of money for one of your own silly ideas isn't it? Too bad it has no basis in reality.