No, I don't think we're all in agreement that the dream scenario was the only way.
Judith Krantz got it right: Following the flatlining, what would happen in ANY movie/show is that nurses and doctors would have rushed in, the family would have been escorted out, and they would have attempted to revive him. Sometimes teams work on a person for several minutes before succeeding or giving up. Even ER featured 20 minute plus resuscitation attempts.
So the episode freezed right after he flatlined... so what? If we are expected to believe Pamela dreamed every single damn thing that happened in Season 9, then why can't we accept that, after the freezeframe, the team came in and tried to revive Bobby? That's all the family would need to know. Katherine or J.R. or whomever was involved in making Bobby look dead. It's a little far-fetched, and not DALLAS' style, but
so was the dream, much more so! Even if they did end with the shower cliffhanger, they could spend the first episode of Season 10 having Pam and Bobby talk about how Bobby woke up in some clinic, he was Katherine's prisoner, a few flashbacks to show his escape and reunion with Pam, voila! It still would have hurt credibility a little bit but the audience would prefer having Bobby back.
There's only a couple reasons it happened as a dream: It was the quickest, easiest (and cheapest) way out, and I strongly suspect Katzman may have wanted to say a big "f**k you" to what had transpired on the show when he was no longer in power. Plain and simple. Not only is he back now, but he will
literally wipe off every single thing that happened when he was gone.