These types of problems roughly map onto the distributed identity problem: there's no known way to distribute `K` authority identities to `M` trusting identitie

These types of problems roughly map onto the distributed identity problem: there's no known way to distribute `K` authority identities to `M` trusting identities without some kind of trusted intermediate. "Vouching" can form that kind of trusted intermediate, but probably not without grinding an ordinary speedy update process to a near halt. That's probably a worse outcome than just having the pre-existing authority (i.e., Mozilla or Google) establish an enforceable policy around what constitutes an acceptable (or acceptably transparent) update.