Bingowings said:

Just had a slightly bonkers idea.

What if Anakin lost his saber to Grievous at the beginning of the film and grabbed back another saber in the fight on the bridge.

And in this scene Obi-Wan retrieves the Anakin saber he will later give to Luke.

That way you could have Vader fight Obi-Wan with a red saber and still have a blue saber for Obi-wan to give to Luke at a later date.

Genius! - it also means we don't need the horrible scene later on of Kenobi just standing there while Anakin burns, and walking off with his Lightsaber.

And this way the Saber that Luke later inherits is truly the weapon of a Jedi and wasn't used to slay fellow Jedi!!! [and non Jedi]

Please at least consider this, Bobgarcia74