I wouldn't want to be one of those key holders I imagine you would need armed security at all times, and what is the recovery process should one of the key holders pass on or be compromised? 

What is the lowest amount of money a key holder would accept to hand ovr their keys? 

How far would criminals go, just wrenching you or going after friends and family?

Like you say a trillion dollar pay off brings all sorts of elements out of the shadows and willing to put in considerable time and effort to come after the weakest part of the security model, which is those people.