Seeing this makes me also think... why not offer a service that will lock down all finance, identity and other related services upon the event of a perceived attack? Sure, it would be worthless if it was too sensitive. I key feature would be that it could be unlocked in 5mins or less by an account holder.
this would be vulnerable to DOSing. Imagine me, your competition, with a finger over a button that can make your money useless for the next five minutes.
This. Unless you are a mayfly, you are highly likely to outlive any new business. Simpler approach is to have an executor have a way to access a password manager to be able to identify and close out online services.