I’ve done this a bunch in the past, and one “gotcha” I always run into is http://example.org → https://discourse.example.org.
Depending on the redirect, it can lead to messages in the browser saying it is trying to connect to an insecure website.
To get around this I use a redirect service that provisions an SSL cert for the redirect, via my registrar at Gandi. They call it “web forwarding”.
Make sure to test your redirect using different protocols (HTTP and HTTPS) to see how it works for your site visitors. 