you know that attack vector is real, but it doesn't work like you think it does, (as illustrated by your earlier though experiment) there is a full force assault underway at the moment happening in the open, BlockStream are openly trying to insert the infamous (SPVP) change into the protocol, only the miners need adopt it, and there is a big carrot for them as the new income it would generate is advertised as coming from new services offered by new sidechains, and it is packaged as no downside risk other than a miniscule amount of CPU power and a a few hours of time.

It remains to be seen if it succeeds, both sides seem to be confidant, and it looks like the market has priced in the odds already.  

Time will tell if its a viable attack vector. as far as i can see it's now (over the next 2 years) or never as entropy has a way of closing such windows. it's time to wait and see