The battles in battlefront were never meant to be accurate to the books or movies. It's more of a game to provide an atmosphere/playground/battlefield where you can have any battle against any faction. For instance... Clones don't belong on the DeathStar. Clones were deactivated by the time the deathstar was built... and the republic had become the empire.
SWBF3 could and should be an expansion pack to SWBF2. I thought SWBF2 could have been an expansion pack to SWBF1 as well though. But as Pandemic isn't doing it and it's an entirely different company that would be doing it (If such a project existed
) a totally new format for the game may result.
They could go beyond the movies and into the books for battlefields, but I don't think they'd have to. They could use just the movies as they've basically done so far. I don't think they've hit every avenue of every battlefield.
I'd love to see a really decent Space Deathstar battle. One where you could take out targets on the surface of the deathstar with strafing runs into the trenches as well. Enemy ships could play more of a defensive role for the deathstar. SWBF3 could also include unlockable ships for space much like the unlockable units or unlockable jedi they have now. The ship would sit in the hanger and you wouldn't be able to board it unless you you had a certain score for the map.
Another battlefield addition could be bringing Bespin Cloud City back and doing an expanded Cloud City Map. The map in SWBF1 was awsm and is still one of the most popular among the SWBF1 crowd. The GameToast Conversion pack does have a converted Bespin Cloud City for SWBF2.. but it's the same map as SWBF1. I'd like to see an expanded map like they did for Kamino from SWBF1 to SWBF2.
I wouldn't mind seeing an expanded Tatooine map as well. One loaded with Tuskens like in SWBF1. A corruscant city battle would be awsm. The current one is just the Jedi Temple.. but how about one that incorporated more of a gorilla style warfare in the streets of corruscant. There's an awsm mod for this in the PC version but is an awsm idea for SWBF3.
There's so many possibilities with just using the current movies as the base for the battlefields of the game... I don't think they'd have to go into the books to look for them. The campaign/story mode of the game could be made up... or follow a book story line... it wouldn't matter to me either way.