Oh these all sound like such good ideas!
Given my knowledge of the Hetalia fandom and how many different stories I've seen pass by... I have to say out of these four the Circus one has to be the most intriguing.
For one, you don't see many circus type story lines drifting about and the summary here really caught my eye.
What kind of secrets is this circus hiding? I'd definitely read to find out. I'd love to see where you'd take it.
Something dark and mysterious? Something more fantasy oriented? Or will it be a bunch of humor that no one would expect?
And I love the fact that you are including such a wide cast for your stories.
Most people don't include very many of the countries since there are so many to keep track of!