For example, if I wish to send someone payment from my wallet to his wallet, I would like to create a transaction with a time limit window before it will start to be validated. In this time window, I would be able to cancel or modify the transaction, for various possible reasons. Is there any blockchain or wallets with this feature? It seems like this feature should be desirable, and even if it's not natively supported by the blockchain, it should be implemented into wallets?