I've actually played with the idea of the battle not being at the begining of ROTS... to make the battle last longer, and to give another structure to the movie, more puzzle like. Credits are to be given to Aalenfae too, with whom this brainstorming took place:
First of all, it needs to be said that this ideas took place not only as an effort to strenghten the movie but mainly to reinforce Anakin as a character with a mind and dramas of its own. So in this plot, it should be explicited in the scroll that he's left the Jedi Order, because he's married now, and maybe more, he's in service to the Republic as a chancellor/government/senate asistant and both jobs are ethically incompatible or something. I'd go with the married stuff, but both of them, even together could be sucessfully explained in the scroll.
The movie starts with a lone separatist shuttle flying by to a misterious dark planet, it enters the atmosphere. It's Utapau (Bob García actually DID this video, with utapau at night). We get introduced to grievous, but the orgiastic choral music is replaced by some mistery mood piece. The holo dialogue with Sidious should be altered.
The end of the war is near General, Count Dooku has kidnapped the chancellor over their capital, but we need you to lead te battle. After your return, you will send the leaders to Mustafar...
Or maybe: "I'll meet the leaders in mustafar to give shape to our new government"
Now that scene is setting up the structure of the movie, it presents us potencially every act that is to come. And it just recquires dialogue replacement with some good impersonator. This way, we won't get the feeling that the CSI is a faction that doesn't know what to do. And it certainly clarifies things, which is something the begining of ROTS is totaly lacking. While impressive, the current start of the movie is a mess of information, you can't process it, just swallow.
After this holochat, I'd cut to the Balcony scene, the cheesy one we all hate, I think it could work now. There's no baby reveal, the baby coming is a given fact, a natural fact that needs no "Anakin... I'm pregnant" stupid stuff. The exceptional situation with the Chancellor and the siege of Coruscant is presented from inside the planet now, in first person, and that first person is Anakin, who is in struggle about keeping his retirement or coming back, and maybe the dreams are what trigger anakin to return to the Order and help the republic.
Some things would acquire different meanings this way. Padme's stupid cry for them leaving to naboo and "leave everything else behind" is now under the crystal of a sieged city. And his pregnant woman and yet-to-be-born child is a strong cause to make him go to war. The exagerated sugar of the scene should be compensed by this fairwell sense, at a point.
Next scene should be Anakin meeting Obi Wan in the Jedi control room, we also got that scene, with holograms that could be replaced into schematics of the tactics to be applied in the battle.
Then, we shall need some aire, so cut to something else, more quiet maybe the rebellion scenes. It'd be curious to have the rebels meet while the Chancellor is captive, very figurative. The scene ends, and drums... the sun... camera pans down... the star destroyer and the battle of Coruscant.
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Other thing to be put here was to make the characters make their own decissions...Luke decides to go to Bespin, and the core of his drama is actually in making the good or bad decission, while in PT it's all destiny in the sens of greek drama, Anakin is constantly driven, and that's wrong. Little decissions can make big changes in our perceptions of characters. Here goes one, also with Aalenfae:
Anakin and ObiWan should chase Grievous after rescuing the Chancellor. No ray shields, it's not that they got caught, but that they took the decission to go face him. It's not a rescue mission anymore, it's a secret mission, with many objectives.
The way it is currently, it's like they are on the ship, they fall in the ray shields and since they're protagonists everything turns just fine when they face Grievous.
How to do this change?
Have Grievous say something about it, or maybe the battledroid, we got the security camera footage of them running through a corridor... then only the simple replacement of the line by the droid to "they're coming here" and Grievous saying something along the lines of "Skywaker, nice challenge" and voilá.
Cheers!