I really think Tinman ended up being a hi-light of the game.. Of course, I might just be horribly biased haha. But for someone who wasn't even set to appear in the original concept he ended up playing a very pivotal role in the final product.
As for how he interacts with the games mechanics, well, he wont "follow the rules" so to speak. The perks of being a machine is that you don't have to deal with stamina. He doesn't need food either but that'll be where he gets a bit tricky. The items that work on Red won't be compatible with him. You'll instead need to find oil to keep him running. And of course he'll interact with statuses in unique ways as well, being immune to things like Bleed and Burns. In theory he's a very powerful character but his health will be a lot more finite than any other playable character.