I'm not a network engineer but I believe Tier 1 and Tier 2 networks are needed for the Internet to exist. They do not act as a central authority, but the Internet itself needs them to work like it do now.

I simply do not understood what you wanted to say by your last paragraph.

EDIT: To clarify my point is that I believe the internet is poorly decentralized, it simply means some guys has too much power to shutdown traffic from entire networks to even reach the Internet if they wish or when it's convenient to them, if we ever have another large scale global war I believe this will happen.