Changing body value on the gateway before reaching backend services


I have been using Lua Filters to swap out a custom opaque token on the headers to the JWT in the gateway before reaching the JWT validation policy. Lua Filters currently doesn’t support changing body values of the request, only headers, I was wondering if there is a way to do it. Currently the only way that I can think of is implementing our own envoy Filter, which I don’t want to do, do you know if there is any other way? Can a mixer adapter do this?