CAOD was a terrible forum. People went to places such as SHC and others, to discuss alliance politics instead. CCP put some rules in place, to limit altposting, but it wasn't enough.
CAOD then did what people considered impossible, and became worse. So bad, that CCP made it invisible to everyone except paying subscribers.
The IGS currently occupies a high up position on the forum list. That is open to change. It is visible to guests. That is open to change.
Having some off site RP forum, be it IC sections on backstage, or whatever, means that people who care about RP, will not post on IGS, they might read it occasionally, but they sure won't spend the time to report the terrible posts.
This will inevitably lead to the decline of the IGS, and CCP would probably move it further down the forum, and similar to CAOD, remove it from public display.
That can only ever be detrimental to EVE rp, and attracting newer players.