Well, if you don't want the risk of sounding unnatural, こいつ/やつ are pronouns that can be used for both people and objects, and they are quite disrespectful as well. You can further write those pronouns in katakana to emphasize the distance between you (or whoever) and the object-person. (katakana can both express intimacy and stiffness/foreignness, usually by context you can determine which is which)
You could also emphasize the dynamic between (whoever) and the object-person by using を more frequently than が in places where they're interchangeable, since を implies more control over an object in a sentence according to IMABI
Most other advices I could give involve niche sentence structure changes or grammatical changes like the one I just gave you. I'm not sure there's an easy way to convey the same feeling of "it" in Japanese, to be honest.