I know Area51 is rather different from all other StackExchange sites in terms of code base and functionality, but is there any chance that Area51 will participate in the Winterbash next year? I'd love to wear my hats there too!
We don't have a setting this year that allows a site to display user's hats (earned on other sites) without letting users earn hats on that site. If we did, that's what Area 51 would have, as well as any private betas that start during the event.
It's not going to be possible to implement this for the current Winter Bash event, but we'll certainly keep it on our list for things to consider for next year.