If you’re using Mule and are stuck with RAML then I think you will be forced to neuter one of the tools in some pretty fundamental ways.
How are you planning on having your developers tackle the dynamic nature of response messages which jsonapi provides through many features? One of the primary benefits of RAML was like OAS to better support typing. If you plan to neuter jsonapi’s dynamic message representations, do you gain much by using the format other than normalized resource representations on a standard format?
If you RAML everything as purely a jsonapi message, don’t you lose many of the tools intrinsic benefits?