I made a typo in my original question: I was afraid of taking the services offline, not online.

Gotcha, that makes more sense.

If you try to run the reverse proxy on the same server and port that an existing service is using (e.g., port 80), then you’ll run into issues. You could also run into conflicts with the ports the services themselves use. Likewise if you use the same outbound port from your router. But IME those issues will mostly stop the new services from starting - you’d have to stop the services or restart your machine for the new service to have a chance to grab the ports while they were unused. Otherwise I can’t think of any issues.