I might be interested. Do you have any specific plot in mind? I thought I would be most interested in a mermaid, which is still interesting to me, but honestly, I'm thinking a werewolf plot could be intriguing. It's the only one of the four I've never done a story with.
Mixing the two would work fine, depending on how they're mixed. A story involving both werewolves and mermaids is interesting to me, but a were-maid is less interesting. I'm often wary of adding too much to any particular character.