Could a 2/3 majority vote be used as a consensus
Your proposal is not sufficiently specified:  


How is the authoring node selected?
How does a node prove his authority to author a block?
How do other nodes show support for the published block?
How can the support for a published block be verified by other nodes?


It is not clear how your proposal achieves consensus at all. Additionally, there doesn't seem to be a significant cost associated to vote on blocks, so the proposal is vulnerable to Sybil attacks.