I think you're misunderstanding the meaning behind a 51% attack?
An honest network participant will accept the chain with the largest accumulated proof of work. This is necessary to resolve forks of the chain, which are a natural occurrence.
A 51% attack means that the attacker can create a chain with more work than the rest of the network.
The idea that you can say "we require 60%" makes no sense by itself - you have to say what you actually mean in the context of a competitive and adversarial distributed proof of work blockchain network...
Maybe you have some ideas how to avoid history-rewriting attacks, in which case you should write a white-paper and launch your own sh1tcoin or ICO (only half joking).
An honest network participant will accept the chain with the largest accumulated proof of work. This is necessary to resolve forks of the chain, which are a natural occurrence.
A 51% attack means that the attacker can create a chain with more work than the rest of the network.
The idea that you can say "we require 60%" makes no sense by itself - you have to say what you actually mean in the context of a competitive and adversarial distributed proof of work blockchain network...
Maybe you have some ideas how to avoid history-rewriting attacks, in which case you should write a white-paper and launch your own sh1tcoin or ICO (only half joking).