I would not change events. The story in the old movies, and in the wealth of PT-era EU material would stand.

There is a wealth of material in the EU which we could draw from, and most of it I consider much much better than the PT movies.

I would instead do my best to show the same events from other perspectives and to show more of other events than those in the old PT movies.

There are many loose ends that could be continued on. I would like to emphasize more the religious and moral aspects. For instance, the controversy and schism within the Jedi order about using living and breathing (although willing) slaves as soldiers in the Clone Wars. I would show more of the Jedi vs. Sith - back story. More Force mysticism. Show how Qui-Gon's belief in the Force is different from the mainstream, and why he is considered to be somewhat of a maverick. I would show the relationship between Count Dooku and Qui-Gon. etc. I would show Anakin's Jedi Trials and knighting during the Clone Wars.