One practical issue with power down is that it can be hidden and powered up into other accounts to vote for witnesses, proposals (SPS) or payouts. Even at a slow rate, a small to moderate portion of 73 million quickly has enormous influence (only 5-10% of it is still easily one of the largest stakes on the platform).

If the decision is made that voting is harmful and unacceptable then IMO you have to likewise consider power down too as a practical matter, until some other arrangement can be made such as putting a trustee in place to ensure that powered-down stake is then only used appropriately when the chain can no longer enforce it.