As others have said, it's not as straightforward because the CID contains a hash of the data's encoding which is not the same as the data itself (files are chunked into pieces to facilitate incremental verifiability and better caching, the encoding supports directories, etc.).
There is also Step Functions Local (https://docs.aws.amazon.com/step-functions/latest/dg/sfn-loc..., it is also integrated with LocalStack). I built it as a side project when I was at AWS, motivated by the same frustrations. The best way to get these prioritized is to request it through your account manager/SA/etc. AWS does listen closely to customer feature requests.
Here is IPFS's master issue for "verifiable gateway responses", which summarizes the technical challenges and progress: https://github.com/ipfs/in-web-browsers/issues/128.