The only thing to be done about it at this point is simply use small channels that can't be economically attacked. Putting a really big fee on the closure transaction would also possibly give a strong chance of displacing the giant tx.

I'm sure some kind of countermeasure will be devised in the future but for now best to just keep channels small like no bigger than 0.5btc maybe, if you aren't very sure about your counterparty, 0.1. In any case, more links are better so 10 0.1btc channels is probably better for the network than 2 at 0.5.