An open world Fullmetal Alchemist game set after thr events of brotherhood similar to Breath of the Wild. You'd create a custom character. And go on a new adventure with a new bad guy. Battle damage would show on your character and overtime fade into a scar, maybe a way to reverse this like a healer from the east or something. There would never be a specific battle mode. And your attack buttons wouldn't include alchemy. Just weaker moves that deal less damage. But work as set ups to deal chip damage while you wait for an opportunity to deal an actual hit with Alchemy. As for Alchemy it would function closely to how the Runes do in BOTW, different types of alchemy, like a spike to damage an enemy or use as a platform. Thinner platforms to slow your fall or stop a charging enemy. A part of the ground rising to work as an elevator or to block off a pursuer. An option to change materials. Solid stone to loose sand. Coal to gold. Sand to Glass, water to Ice Etc. In some battles you could possibly lose limbs. If this happens you'd high tail your ass out of there until you find a safe spot to stop the bleeding and find someone to take you to get automail. I think there would be a way to get your original limb back, with different advantages and disadvantages based on if you have a natural limb or mechanical. Now with Automail. Automail would make your hand to hand combat and movement speed better. But it would slowly break overtime and would need to get repaired once and a while. There would be different levels of Automail engineers, low level automail engineers would be relatively common. That way the player is never wondering around without a limb or broken automail for too long. And can usually get something low to work with until they can get something better.