If this chain is being attacked by colluding exchanges, again, and a 30 day delay doesn't prevent that, what is the chain worth?
A group of colluding actors will not be deterred by an extremely long powerdown period because they can change it.
It happened at Steem.
I think the 30 days delay in voting is a nice solution, people will notice if a stake with a size that can influence governance is powerd up and take action... even with a short power down periods.