Unless I've missed a post, I don't believe that Metro has made an official ruling on the settings re vampires/supernaturals/pets/celebrity. Most likely, I imagine he's discussing this with Pam (and whoever else assists him in making final calls), and taking a look at what we're saying.
For me personally, I too agree with Rica's suggestion of "make your choice, and then leave it the heck alone" option. This is no different than someone saying, "I don't like vampires or celebrity, so I'm going to uninstall LN first."
However, that said, I don't agree with the idea that it should be permitted just because it may negatively impact a player's strategy. Isn't that the point of the challenge, if one is going for HoF? To learn to adapt to changes in the game, for better or for worse? Isn't that what makes it challenging? Otherwise, it's just "ho hum, gotta keep this family for 8 generations, following this precise little flow chart with no variation." We aren't talking about bugs or glitches, after all.