I've tried too to make my way a prequel that keep the revelation vader=anakin. There's two solution for me.
The first one need to delete the duel between anakin and Obiwan in the prequel. Anakin will be killed by a character like 'Saruman' ( a former grand master jedi who decided to follow palpatine for protect the galactic union instead of letting it fall in chaos. This character will be rejected by Palpatine when he will no longer need him, soon in EP3)
In the end of the prequel : The audience believes in the death of Anakin, a grand jedi who ran into the lion's jaws despite the warning of his master.
After that we have two options :
- Obiwan, before the EP1 have already train several Jedi. One of them ( who doesn't named Vader but SAREN, Obiwan tell that name for simplification) will be the guy spoken in ANH. A terrible war is taking place outside the republic. Two Empires clush terribly by using a new technology of cloning. A Alliance of Republic Border System born for counter theses exterior ennemies in case they try to attack them. But without the advice of the Senate, This alliance enter in war and get involved in this war. Secretly it is the cloning technology that they want. SAREN, the former pupil of obiwan, and many other jedi will leave the order for join the conflict. During the war, SAREN will discover the old civilisation of Mandalorians and will use them for win the war. After the conflict, the republic will try to administer the region but the alliance renamed Confederacy, Saren turned to the dark side, and his mandalorian will return there forces against the republic. EP1 start at the end of this second clone war against the republic. SAREN will finally be killed in EP2.
- change the dialog between luke and obiwan.
How my father died ?
'The Jedi have been hunted and killed by the Empire. Your father has been killed by its agent, the ennemies of the force.' ( or maybe another sentences before ... the ennemies of the force).