You neglect the part of the scheme above that's moronic because you spent tens of millions of dollars to attack a chain with less than that much immediate liquidity on any exchange. If you were to spend tens of millions of dollars making lots of ASICs, why not just mine with them like everyone who has made ASICs so far is doing?
If you attack it because you're a state actor who wants to get people to use your fiat money instead of leaving it for cryptocurrency, the liquidity on the exchange is irrelevant.
The only real threat to cryptocurrencies on the scale of BTC is a state actor - or several state actors acting in unison.
Like if the US, the EU, China, and Russia all decided BTC was destabilizing their fiat, they could easily 51% the network - tomorrow.
The NSA alone certainly has enough processing power today even without ASICs:
http://www.wired.com/threatlevel/2012/03/ff_nsadatacenter/all/1If ASICs were needed, spending $1B or $10B to secure trillions of USD would be trivially cost effective to a state actor.
That would be years or decades from now, but its a real threat and one that needs to be addressed sooner rather than later.
I like the ideas presented in theory but my technical understanding of them is a bit limited to offer valuable feedback on specifics.