One consideration: how much input is lost after the end of the attack if you decide to buy a large swathe of PoS coin A, as opposed to time, electricity, manufacturing and transportation costs of ASIC development?

How much of a network do you need to damage before it enters a death spiral?
If you were prepared to dump N% of the PoS network after your attack, what is the maximum N where you're still able to disrupt the network?
Does the same apply to miner attacks?

I checked out your article, by the way. One puzzling aspect is this: look at how much it costs to attack a network per $1 per day in block rewards.
Are we worried about attackers because our block rewards are too cheap, or are we worried about attackers because our security is too weak?

Should ETH raise its rate of return to 30%, since then the total cost of attack would increase. Actually, why stop there? Just make it masternode levels of 30000% rate of return.