I have recently started replaying Dishonored and am really enjoying it(though I wish that there was more room to use the more entertaining abilities and equipment, I personally love the Pistol and think it feels great to use; but that messes with my low chaos). I think a sequel would be great(it's probably already in production). Here's what I'd like to see.

1, Character creation, Corvo didn't speak aloud so allowing us to create our own character wouldn't really change much. When we create them, we would be able to pick one of three background, for example, Disgraces Overseer, Royal Spy Trainee, or Remnant of Daud's Assassins. These backgrounds would provide the same amount backstory that we had about Corvo and change how they were reacted to and what could happen in missions. for example, someone with a Disgraced Overseer background may still have some connections and be able to have someone leave an area unguarded or a door unlocked. Every character you play though would be marked by the Outsider, which would, of course, set in motion the events of the game.

2, Changes to Chaos. For me, some of the Chaos causing events in the original Dishonored didn't make sense or really restricted the way you could play if you didn't want the entire city to go to hell and be an ass. So, killing enemies that attack you would not have an effect on Chaos, killing civilians would raise it, killing rats and weepers would lower it, stealing items form an obviously owned house would slightly raise it, and killing unarmed/incapacitated/or surrendered enemies would raise. Disarming enemies would be a new featured added to allow the player to still get into fights, but be able to end them without death(or having to run away). After an enemy surrenders, you would have the option to leave them(chance of them alerting others), tie them up(able to hide them then), or execute them. Those first two result in lowering chaos. Decisions on what you do to assassination targets and world events(like someone being mugged) would also play larger roles on Chaos.

3, Playstyles/Equipment/Abilities/"Classes", while not including an actual class system, weapons would be split up into groups allowing players to pick the playstyle they want and enhance it through upgrades. These weapon groups would be bows(crossbows, wristbows, and longbows), Rifles, Gadgets(grenades, spring razors, and the like), Swords, and Void powers. Upgrading a weapon with coins would serve as a sort of leveling system(with Void abilities still needing Runes), much like it did in the original Dishonored, but it would be much more varied and provide more effects. For example, after upgrading Pistols enough and becoming proficient with them, you could opt to wield a second Pistol in your left hand. Weapon upgrades would also include special abilities combined with Void powers, which cost both money and a Rune. For example, you could unlock the "Specter Bullet" abilities for Rifles, which would allow you to shoot and control a bullet mid-flight, with rank two increasing your control time and allowing it to pass through multiple enemies. Those who wish to be a true "Void Walker" would also be given the ability to use only Void Powers, being able to wield one in each hand and be given a wider variety of powers. To make this playstyle a bit more viable, the player would be able to get the perk "Outsider's Chosen" after investing enough Runes into Void Powers(enough to "lock in" as it were the playstyle) that would allow their Mana to regenerate, allowing them to more easily fight and complete objectives.

Might add some more later.