I finally realized requests from chrome extension background scripts don't count as cross origin!! Meaning I don't have to serve the app locally anymore!
After too much fiddling, I can say that at least by default cors requests don't work on service workers. But we confirmed it worked on extensions so we can still ditch the proxy!
I finally realized requests from chrome extension background scripts don't count as cross origin!! Meaning I don't have to serve the app locally anymore!