I have a steampunk Tinkerbell
I've worn the last few years that I might bring to D*C this year, depending on how the rest of my schedule works out. My brother and his wife are also coming to Dragon*Con for the first time this year, and are planning on wearing steampunk Meg and Hercules costumes. If there's a meetup/photoshoot for steampunk Disney we'll definitely have to add it to our schedules!
I would caution against letting anyone "claim" a character though. You'll get a bigger group and more crowd attention if you allow duplicates. And because steampunking a character is so subjective and could go so many different ways, no two interpretations will be identical. The big fandom meetups always have multiples of the same character (and sometimes a dozen or more of the same character at the really big shoots) and no one minds.
I would definitely be interested in a big meetup where anyone with a steampunk Disney costume is welcome, but exclusionary only-one-of-each-character meetups really aren't my thing.