But you are wrong, it would absolutely not work. The only way to make sure no one has 51% and no one can simply get 51% (buy cloud computing for example) is if the 51% is more than what feasibly can be bought or it would at least need to cost more than what you could gain from a double spend.

Also its about hash power not number of miners, that's completely irrelevant. 100 or 1000 miners that means nothing.