Sorry to revive this post but I wanted to add my info.
I was watching the commentry by Peter Jackson and the Writers on the RotK DvD.
The idea was that Sauron wouldn't physically be there, but it would be more of a hologram or illusion that Aragorn would fight.
Not only that but it wouldn't be Sauron in his big epic black armour it would be the elf version, him former self and that they were going to make him the most beautiful man in all of middle earth. Kinda like Galadrials counterpart.
The form he used to decieve the Elves was called 'Annatar'. The scrapped film footage would have Sauron come forth as Annatar, blinding everyone. Then he would change into the 'Dark Lord' version and battle Aragorn - at different points in development it was literally him, then it wasn't, etc. (the idea is rather silly anyway)
All of this is mentioned and described in detail with the Special Edition.