Eric, I am open to working with you on making proxy a default.
Can you do a local Discourse install, then enter your container and mess around with nginx conf until it proxies correctly, once you get it going paste the nginx config section here and I can look at integrating it. It will take a few months to move to local proxy by default cause everyone needs to do a rebuild to get nginx changes.
BTW, for everyone playing along at home, I’ve created this pull request to implement avatar proxying. Testing would be appreciated; success/failure comments on the PR preferred.