If the witness's from 21 down could come to some consensus with a blockchain version that suits the community and everyone ran the same version. Then in effect you trap the 20 fake witness's SP or at least the exchanges into holding steem power. So they are unable to power down without been removed from the top 20 positions.

So in effect you get all the community to vote for 21 to 41 in the witness list
Plus get everyone with steem on the 3 exchanged to withdraw their steem