Rune, you crazy guy, this looks like a very clever idea, but my gut tells me it would never work. I'll see if I can convince my gut to tell me why it's so pessimistic, but first a question: When a mining pool publishes an ERB, do they collect the normal bitcoin block reward for it as well as the future reward they get at exodus?
I think that would be a bad idea, as that could allow for the selling on of ERB's and would perhaps make it less obvious when the bitcoin blockchain is ready for the exodus (when every other block is an ERB). If miners are forced to hold onto the normal bitcoins in the ERB if they want to collect the bonus bitcoins post-exodus it will make them more vested into seeing the exodus go through, I think. I'm not sure if it really matters though.
The way I see it would work is this: When the bitcoin network stops and the new genesis block is created, the developers who make it basically manually go through a list of all ERB's they can detect that fulfill the rules of the social contract (no transactions, the word "bitshares" embedded into it). If the 25 bitcoins still sit in the same address as when the block was mined, they are manually changed to x times as many, creating the bonus bitcoins out of thin air and allowing the miners to claim them just like they claim all their other post-exodus bitcoins.
I guess the we would vote the new genesis block into effect, we will all attempt to go through the block and make sure everything is according to the social contract, so that the transition is as smooth as possible with no errors (any error would cost us dearly, and would mean we would have to be very careful). It's possible that we would have to have the bitcoin network shut down for at least 24 hours just to be totally sure that everything is as it should be, before we vote the genesis block into effect. During this time exchanges would still work, and anyone needing to do blockchain transactions would have already moved over to bitshares as it would continue to function normally. Hodlers wouldn't need to do anything though, they could just wait for the exodus to happen and claim their new bitcoins whenever they need them. In case the new genesis block is wrong and isn't accepted by the miners, or is too slow, they would resume processing transactions on the bitcoin network and the exodus would fail, so we will have to be swift and effective. A failed exodus would hurt bitcoin a lot more than it would hurt bitshares, so there is no chance this will be used as some angle of attack - if the exodus is about to happen then the bitshares market cap will already be at 1 billion USD.