Forgive me if I'm misunderstanding, but I disagree with you.
A merkle tree is a recursive structure. If you trust a substructure of it, then you don't need to repeatedly re-evaluate that substructure. What that means in practical terms is if the merkle-tree entry summarising the state of the chain as it was a year ago is assumed correct, then you don't need to keep any of the transaction data from before that point.
But this can only work if you don't have to look back. In Bitcoin, every transaction references an arbitrary previous transaction to prove that it has sufficient funds. You would therefore need "checkpoint" transactions that say "This is the amount of money everybody's got now; we can now forget the past".
It is possible to create new transaction outputs using old UTXOs, hence nodes can do its own checkpointing if they wish, with a loss of transaction fee.
you are misunderstanding. you're given a state of accounts and it has "correct" signature (according to a third party) - without verifying every transaction that contributed to building that state you cannot be certain it doesn't contain invalid records. merkle has nothing to do with it, you either verify or you trust a third party.
checkpointing ethereum state or checkpointing bitcoin utxo set is a way to trade away security, decentralization and trustlessness for faster bootstrap. and ethereum folk have become way to relaxed about that fact.
A merkle tree is a recursive structure. If you trust a substructure of it, then you don't need to repeatedly re-evaluate that substructure. What that means in practical terms is if the merkle-tree entry summarising the state of the chain as it was a year ago is assumed correct, then you don't need to keep any of the transaction data from before that point.
But this can only work if you don't have to look back. In Bitcoin, every transaction references an arbitrary previous transaction to prove that it has sufficient funds. You would therefore need "checkpoint" transactions that say "This is the amount of money everybody's got now; we can now forget the past".