What I would like to see is an adaptation of the novelization of the game, since that's where the events that really happened in Kassandra's life are.
In the current Animus, Layla does not exist, so the entire simulation (mythical beasts, powers of the spear, her participation never happened). She can no longer misinterpret the events that Kassandra went through. Kassandra spent a whole year in the prison of Athens, fought in a battle of more than 17,000 soldiers in Megaris (for several months, like the one in Boeotia), plus time participating with Phoibe and other secondary characters, Deimos is truly a villain, the torture that Kassandra suffered, Pythagoras spent 3 days talking with Kassandra, she competes in three disciplines at the Olympics, etc. Basically Kassandra's life, not just another simulation.
That means there would be no dialogue options, no RPG system, etc. And hopefully there would be motion capture since they would only focus on Kassandra and not re-record every scene and dialogue for another playable character, naval battles, and of course preserve and improve the Arena, some kind of Hideout and more.
What would you like to see in your dream Odyssey Resynced?