Every source I've read, including the Bitcoin whitepaper, states that the blockchain scheme is necessary to achieve consensus and protect against double spend attacks and 51% attacks, among others. But because nodes possess their own copies of the distributed ledger and transaction history, they aren't subject to 51% attacks. If Bitcoin didn't have a blockchain scheme, all nodes would still be capable of validating transactions, updating their own records, and syncing with their peers. The order of transactions is implicit and doesn't need to be forced.

A better way to achieve consensus, and without flooding the network with messages, is for acceptance of transactions to happen in silence. A response is only necessary if a node rejects a transaction and the only reasons to reject a transaction is either because it's invalid or because a double spend is detected. When a transaction is invalid, it will most likely get rejected by the immediate peers of the node that originating it and it will not be relayed. When a transactions is one of a number in a double spend attack, it provokes a rejection message that spreads throughout the network and cancels them all out. Wallet software should provide the user with an average wait time based on latency statistics of the network. If a recipient hasn't received a valid rejection within that time, they can safely assume it's been accepted.

There's also a better way to manage inflation and deflation without creating or destroying wealth. You simply multiply or divide the current supply by exchanging it with a new variant of the same coin at a certain ratio. Variants of a coin can be distinguished by a color association. So if the current variant is green, the next variant may be red. An exchange ratio greater than one-to-one (>1:1) would facilitate deflation while an exchange ratio less than one-to-one (<1:1) would facilitate inflation. As long as merchants observe the transition by adjusting their prices according to the exchange ratio, no wealth is gained or lost as a result of the exchange.