Hi, I'm not sure where you get that "All previous states do need to be kept if you aim to audit the chain..." but you are wrong. We only need to keep the block

Hi, I'm not sure where you get that "All previous states do need to be kept if you aim to audit the chain..." but you are wrong. We only need to keep the blocks with the transactions which are replayed every time you sync a new node and all (edit: intermediate) state transitions are re-created from the genesis file until today. For most cases, the cryptographic guarantees you can get synching only the block headers as a SPV node are strong enough. Think of it this way, let's say you are obligated to carry 1 valid photo ID with you. Would you carry only the latest and valid version or would you carry every single issue of, let's say, your passport? Speaking of perspective, Visa exists since the late 50s and Ethereum for about 5 years. The next iteration of the network will be focused on scalability and privacy technologies and we will surpass the 1000 tps on-chain and have the off-chain capability for millions of tps.