If one had the entire saga to reboot, surely the story would be quite different. You could seriously iron out the kinks and apparent retcons.
Would one be obliged to stick to certain key points?
Only one Death Star. ROTJ’s battle centers around a fleet or an attack on the Emperor’s person on Coruscant. No Starkiller Base, either.
Anakin’s origins are shrouded, with no virgin birth stuff. Prophecy is fine, but it would later be subtly implied to be a sort of ongoing thing, like anyone can be anointed as a chosen one by their actions.
Rey Nobody, to go along with the above.
We get to know the Sith with exposition and seeing them scheme, perhaps with Plagueis being the shadowy villain for TPM. We should have some sense of their history.
The third trilogy would delve into mystical aspects of the Force and balance, perhaps letting us know the Whills. Something to elevate them thematically over what we already saw in the second trilogy.
Really, though, if I had 9 guaranteed films to sketch out, I’d let 1-5 be similar to what we know of the existing saga at their basic plots, and then replace 6 with a 6-9 worth of stuff as Luke finds his lost twin and faces Palpatine in an Ep9 showdown.