The proposal aims to enhance the resilience of the Bitcoin structure by utilizing existing mechanisms without introducing new elements. A key focus is on the use of the "nLockTime" feature, which is typically set to zero but has the potential for a novel application. By incorporating the sending timestamp into the "nLockTime" field, it's suggested that transactions can signify their readiness to be included in a block immediately, leveraging legal and existing functionalities of the Bitcoin protocol.

Delving into the technicalities, the current method for organizing transactions within the mempool—the memory pool where transactions wait before being confirmed—is highlighted. This process relies heavily on a fee rate-based system facilitated by the Boost MultiIndex's indexed_transaction_set data structure. Transactions are prioritized based on the ratio of transaction fees to transaction size, allowing those with higher fee rates to supersede others in the queue for block inclusion. The dynamics of adding and removing transactions from the mempool are controlled through specific functions, such as the TrimToSize function, which manages the mempool's capacity by prioritizing transactions according to their fee rates.

The proposed intervention introduces a dual sorting mechanism that considers both the transaction fee rate and the "nLockTime". This involves updating the indexed_transaction_set to include a new comparator that balances these two factors. In practice, this would mean adjusting the TrimToSize function to not only prioritize transactions with higher fees but also give precedence to older transactions based on their "nLockTime". This approach aims to ensure that transactions with lower fees but older timestamps have a better chance of being included in a block, thereby reducing the likelihood of transactions stagnating in the mempool due to low fees.

In conclusion, integrating "nLockTime" based sorting alongside the existing fee rate criteria proposes a more nuanced transaction selection process for the Bitcoin mempool. This methodology seeks to balance efficiency with fairness, giving older transactions a fighting chance for inclusion despite the competitive fee market. Such changes advocate for a cooperative nature within the blockchain ecosystem, challenging the purely competitive narrative often associated with transaction processing.