How does the JSON look like; could you share an example?
How do you want to map it? Can you give it a try and then get back to us if you get stuck?
How do you want the report to be generated, in what format, and with which preferred services? Can you provide an example template you want to use?
When you have a scenario, do share the blueprint here so we can provide suggestions on how you can further optimise the flow.
If the external service has a Developer API Reference/Documentation, then yes, you should be able to integrate the endpoints in Make using the generic HTTP “Make a request” module.
You can also suggest for it to be made in the Idea exchange. Don’t forget to search for it first, in case someone already suggested it!