Allow me to weigh in.
R* is probably the dev most familiar with the ratings board, and the guidlines of the console manufacturers. R* are the guys always pushing the envelope and they've been burned before. They are a very rich group of people [edit] who I am sure can afford lawyers [/edit] and I am sure after Hot Coffee, everything that goes into the game is thoroughly discussed before management.
Correct me if I am wrong, but submitting a game to be rated involves creating a video of all the gameplay elements to be viewed by the ESRB. So R* can in this regard make their game seem worse than it is.
I'm reminded of an old filmmakers trick, where the filmmakers would edit in violent, gratuitous acts that they never intended to make the final cut. When they ultimately got back their NC-17 rating, they would take out all that footage and re-submit the film and act as if they spent all this time and effort to make the film more palatable.
Now the delay until September is worrisome, but the cynic in me says that that's just a ploy to try and give the illusion that they're working hard on retooling their game.
I just can't believe that R* would have actually intended for a sex scene involving a corpse to be part of the gameplay, and that they would have been unaware of Nintendo's policy of no AO games. Hot Coffee was a lot less than that. I think the only answer is that R* felt that this game was a borderline candidate for the AO rating based on violent content, so they threw in something truly offensive, then delayed the game so that they could give the appearance that they're striving to curtail the offensive parts of the game, so when they ultimately re-appear in front of the ESRB they can present the great job they did in censoring their product.
Plus all this AO stuff is GREAT publicity.
And on the subject of a private ratings board rather than a public one...
If the government rated games (that would be the best job ever, by the way, government jobs are sweeeeet), then the raters would have to be above influence, they would have to provide full transparency and a list of standards, there would be a legal route for appeals, free speech would certainly enter into it, there would be an ombudsman etc.
I think the idea of a private board free from political tampering is just dandy in theory, but it's been an abysmal failure for movies. As a minor I was able to read books like Lolita, and visit galleries featuring nude photography, but I couldn't see the '97 film Lolita. Books and art are subject to government censorship, but it's rarely exercised, and successfully censoring a work had proven very difficult in the past. Movies and games are censored constantly.