It's brilliant. And a bit reckless. I think we can achieve the same ends by being a little less hostile. Why not let BitShares grow a bit and the market progress naturally, to the point where there are open questions in the crypto community (not just from us) about whether BTS should succeed Bitcoin? And then prepare some sharedrop on-ramps to buy us some more Bitcoin defectors, accelerating the domino effect just when it can have the greatest impact. That way, it wouldn't need to be quite as hostile/radical and we'd be giving people the choice of jumping ship for some incentive. Plus, they might actually WANT to come here rather than being forced.
If this attack is possible, and we don't do it, then someone else will simply do it. The worst case scenario I can imagine is that it's simply one of the big bitcoin pools that decide "its time to upgrade bitcoin", then fork the bitshares toolkit and allocate 10% of all bitcoins to themselves on the new chain.
I think people are vastly overestimating the power of internet shitstorms when it comes to determining prices. The most lucrative companies in the world are also often those with the most disliked business practices. People invest primarily based on expected profits, with a (loud) minority being the religious fanatics we know and love from /r/bitcoin. If this attack is possible and any coin/blockchain announces they are going to perform it, they are going to be a serious hot commodity among traders who trade based on profit seeking (which is probably the majority of traders). In the long run we will not actually hurt bitcoin holders (total inflation will be lower), we will give them a massively improved system (bitshares), and we will finally give them control over their own coins, making it impossible for this kind of attack to ever happen again. Also this is a chance to actually make sure bitcoin survives through the ages and never goes away. For me at least this is very important. I think many bitcoiners who know in their heart that POW cannot be upgraded also will be quite quick to realize this, because before it was a very real possibility that bitcoin would simply die out once second generation blockchains begin to compete.
If it isn't us who does this, someone else will. They will likely give a more unfair distribution to bitcoin holders, and then they'll turn to us, fork our unique features, and destroy us. If our stakeholders think that our 20% valuation is too high, then maybe we should put it at 10%. It would still be an approximate 1000% increase in value at current market rate and thus would be massively profitable for bitshares holders.
The only way this can be presented and framed to the bitcoin community is with the obvious fact that we have to do it so someone else doesn't do it before us. We're migrating the bitcoins away from POW because it is vulnerable to this attack, and they will risk getting an even more unfair distribution, with even more going to miners, if they resist us. The initial shitstorm will be immense but once people realize that this attack vector exists they cannot deny that POW bitcoin is going to end, one way or another, and when that happens it might as well be bitshares that they migrate to.