[@Raizin] Well, a chain's loudness would depend on the material and fineness of the links. They can produce a nasty noise or simply a subtle "SSSS"-kind of sound. In the end it's up to you, but keep in mind that this is supposed to make fun of RPG stereotypes, so I think you'd be safe.
About the inventions. I like the idea of having a tinkerer around, and with a little imagination that can provide some really funny moments. But since you are an assassin as well, try to stay away from the hidden blade from Assassin's Creed, too many people rip that off. Have a look at the drawings of Leonardo da Vinci for inspiration.