In an early piece of promotional art for the Bloodline DLC, three silhouettes can be seen - a red one, a green one, and a blue one.  The red one turned out to be Aiden, the green one turned out to be Wrench, but the blue one was strangely removed from all future promotional art, never to be seen again.  It turns out this was going to be Jackson!  He was not only going to be playable, but also be a completely different character and have a much bigger role in the story.  However, this was reduced to a short P.T. styled walking segment where you can't even open the menu.

If you could, though, you'd see he has a proper name, but a randomized job, Wrench's bio, and no skills.  He has no voice actor outside of Bloodline missions either.  This mod adds Jackson to your Campaign team after completing the City of London borough uprising mission.  He comes equipped with a custom loadout which resembles a kind of "main character" setup, consisting of Bloodline abilities and normal game abilities.  If you go into the wardrobe, he has the mask he uses during the Rempart escape sequence, but strangely the mask can disappear from the wardrobe, no idea why.  He's fully customizable too, meaning you can make a crazy-looking Jackson if you want.  As a side effect of having no voice actor, conversations taking place while controlling him will sometimes "speed up" since voice lines are tied to animations and his finish instantly.