A Bioware type game set in a Tokugawa Japan style world of islands like Windwaker.Snowy fields(like Hokkaido), forests of cherry blossoms(an epic version of Sakura Namiki street) and vast jungles(like Yonaha Dake)would be only part of the landscape.
It would have complex gameplay in real time, custom classes, realistic healing and injures, customizable weapons, a customizable character with a chosen first name, water/food/sleep bars, a base wooden ship where your weapons, armor, other items, and people not in your party would reside, story choices happening during gameplay(i.e killing a person or sparing their life would change the story) along with the ability to talk your way out of combat, amazing A.I that reacts to light and sound, martial arts, animal hunting and skinning, loads of stealth mechanics like hiding in objects or deceiving groups by stealing their uniforms in infiltrate and even hiding atop of walls and ceilings,day/night and season cycles that would change a missions structure, fully explorable cites with thousands of NPC's in total, a whole lot of side-missions,and a fully voice acted story.
It would also include AAA graphics along with an amazing art style and an unbelievable amount of choice, including the ability to create your own party of up to four characters. The main character is a shamed Samurai who failed to protect his master from a hit. He decides to scour the land in search of adventure. He then hears that his old master is furious of his parting so he seeks protection by either joining the emperor's warriors specialized in straight up combat, a shady rebel group led by a disgraced family of nobles seeking to take down the emperor for personal reasons, or take his chances and go rouge, following no one. And it would have to be topped off with an amazing ending
TL;DR: A badass WRPG that is never going to happen.