Sounds similar to the mini-blockchain implementation pioneered by Cryptonite:
https://bitcointalk.org/index.php?topic=713538.0The "safe box" could be compared to the mini-blockchain radix-tree-based balance sheet, where the hash of the safe box is embedded into blocks, so that a user's copy of the safe box can be validated against the blockchain.
If it doesn't need historical operations then why does it need a blockchain? What makes it different to other coins? Does it have a blockchain pruning mechanism to keep the blockchain small, or some special features besides being written in a different language to other coins?
As far as why it needs a blockchain, I would assume the blockchain acts as a means of maintaining consensus on the contents of the "safe box" although it isn't referenced directly for transaction history/data/validity.