Vanilla is a product of Lussumo:
Documentation and Support.
I think the writing staff may have written themselves into a corner where you *couldn't* have a big, scary vampire on the show anymore, without introducing a whole new breed of vampires like they did in the final season or vampires with a new set of powers in the Season Eight comics -- because they'd left the audience laughing at them for so long.
No offense intended because we're just kind of brainstorming here and the more opinions, the merrier, but... you talk about a lack of imagination and give us redundancy -- take a scary, evil guy and... uh... make him scary...and evil.
The Gacy or Amin types are nasty enough as is, adding vampire to the mix adds very little - -they're already monsters. It just seems pointless.