the moderation is going to be the problem.
doesn't matter what forum profile is used, there's going to be only a handful of actual people behind the controls.
so, there's always going to be the suspicion that A is held to a different standard than B, because A is in the same corp as one of the forum staff, and B is not. We've already seen that discussion enough times here, about how some posters (some of which deleted their account), regularly posted stuff that ended up catacombed, and never seemed to face any consequences, in some cases seeming to receive praise from forum staff, while other posters do something once, and seemingly get banned, or at least publicly warned they could be banned.
So, that situation does not lend itself to a tight rules regime for the forum.
But if you have a loose rules regime, where only the most uncontroversially unacceptable posting gets moderated (pornography as an example), then... that rules regime isn't really any different from the IGS.
so what happens ?