You are definitely not getting my point here. From what I can tell of what happens in the books, Jackson has already bent them or added to them enough already. Most importantly he added a LOT of stuff about Saruman to the first and second films, he built the character up, he made him important, he made the audience want to see him get it at the end of the film. Of course Saruman survived and the audience doesn't get to see the payoff of Saruman being "vanquished" however it is done. What happened in the books is very unimportant to the movie.
Look I'll give you an example. The character of the Uruk-hai Lurtz wasn't in the books, another thing Jackson has added. So in FOTR, Lurtz was built up to be the "leader" of the Uruk who attack the Fellowship, and he was designed to be an apparent figure for the entire group of Uruk that attacks. The audience sees him, begins to dislike him. The Uruk-hai attack and Lurtz is the most apparent attacker in this respect because he's the only one the audience in any way knows, so he bears the brunt of audience hatred. Then Lurtz himself pierces Boromir with 4 arrows, providing an even greater need within the audience to see this character truly destroyed and then BANG Aragorn decapitates him, and story is paid off, and audience feels happy because that has happened. Not happy because the story ended happy, but happy because the story ended.
Now compare this with Saruman's (of the movie, forget the books exist) story. When we first see him, we don't know he's a bad guy, thinking that because he's a wizard like Gandalf he might be good. So then Saruman attacks Gandalf without warning, and nearly kills the guy, but he doesn't. Instead he imprisons him and "tortures" the man. Then he destroys a whole load of trees, and begins to build a massive army of ugly looking things called Uruk-hai. He also tries to thwart the fellowship by changing the weather and nearly killing them on the mountains. Then in the second film, we see a lot more of him creating armies which then go and attack Helm's Deep, nearly killing our heroes in the process. Now forgetting about the books, what we should see now should be some sort of scene where Gandalf gets revenge, vanquishes Saruman and then rises to become Gandalf the White, and the story is complete with regard to those two characters' battle with each other. Now because that didn't happen we have the situation where we still need that payoff for Saruman. I'm not worried about not having payoff with Grima, because he was only in it for a short time, and not built as such a major threat. But the man who creates the Uruk armies, nearly destroys Gandalf, nearly kills the Fellowship, and senRAB the Uruk to destroy the people of Helm's Deep, neeRAB a payoff, neeRAB to be killed/stripped of his power/magiked away. But no, we're left with what happened in the Two Towers? Perhaps this is all a rumour blown out of all proportion, or indeed a coverup by Jackson, because otherwise it'll make sure one part of the story makes very little sense at all.