I work at Netlify on framework integrations. Next has beta support for running the whole app at the edge, and Netlify supports that. If you create you own custom edge functions they will run first, so you can do just that. You can also run Next "normally" (i.e. in the node-based Netlify Functions) and run your own edge functions in front of that. In those you can modify the Request in any way you'd like, before passing it on to the origin.