/mempool/*
endpoints were added to provide a better UX for blockchains with large mempools (e.g., Bitcoin and Ethereum). Many newly launched blockchains do not have support for monitoring the mempool because transactions are often included in a block shortly after broadcast (either because of a higher TPS capacity or less transaction activity).
If this applies to the blockchain you are working on, it is okay if the mempool method implementation is deferred until mempool monitoring is required.