One radical change that popped into my mind the other day was replacing the Gungans with Mon Calamari (I said it was radical).

Almost impossible to imagine how it could be done but just how many sentient amphibious lifeforms does the saga need and it would make us care more about them in Jedi if we met them back in Episode One.

Jar Jar is largely redundant in almost all the films bar the first one (where his unique manner is almost universally loathed) but if he was the young Ackbar we would see him as a founder of the Rebellion and instrumental in the Empire's downfall.

I realise that it would be easier to replace the Mon Calamari with Gungans in Jedi but Ackbar looks so much better.