Loading select accounts from a BAI into Cash Management

We are in the process of moving from on prem to the cloud. We are only planning on configuring a subset of our bank accounts in Cash Management in the cloud. Is there a way to tell CM to ignore certain accounts? I am being told that in order to only load certain accounts, we will need to get the banks to generate custom BAI files that only include the accounts we have set up in CM or use a ETL tool to strip out the unneeded accounts prior to the file getting to CM. This does not seem correct