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?

edit:
For instance, your net profit per day right now mining Bitcoins with 80 TH/s (enough to attack the network) is $530,445.73 (after power given a mildly inefficient ASIC).  Why would anyone in their right mind perform a 51% attack when they're making that much per day off their hardware?