There are some people who are more hardcore set in what they think steampunk is than I am, so you might get some nay sayers, but I think you jumping off on the right foot. Especially the little jacket. I did that for my friend's steampunk costume
I designed and made for her a few years back. She still wears it and even had the steampunk band Abney Park compliment her costume, so that was really cool.