As with all my mods, my practice is firstly create a good base then build on that.

With my Simple Vampirism Expanded: http://tesnexus.com/downloads/file.php?id=36408

• (1st release:) reversed the effects of Oblivion's feeding: stronger when fully fed, weaker when blood-starved and other tweaks
  
• (next incremental releases:) added Vampire experience level and "gifts" (offessive and passive abilities that progressively get stronger)
  
• power of suggestion (NPC follow me, go to sleep, wait here)

I'm now at the point of adding the ability to feed on actors (npcs and creatures) that are unconscious, paralysed or dead.

(By the way, my inspiration for this mod comes from the movie Interview with a vampire.
My knowledge of vampirism is fairly generic: from general lore and movies.
I've not read any books about vampires nor have I played any other games as a vampire (e.g. Vampire: The Masquerade - which was apparently good).

What penalties would the player vampire receive when feeding on dead blood or on creatures? Or benefits?
Currently, my ideas are:

• No penalties or rewards for feeding on npcs that are unconscious or paralysed.
  
• Reward of feeding on the newly dead (within 15 in-game minutes of death):
  delay the onset of the next stage of Vampirism.
  In SVE, the stages of vampirism increase at exactly 24 hours from when the player feeds.
  E.g. if the player feeds at 8AM, the next stage will occur at 8AM the next day.
  Feeding on a dead actor will delay that onset for up to 24 hours - depending on how long the actor's been dead.
  Feeding on a creature halves that resulting delay.
  Formula for the delay is: 24 - time dead / 15 minutes * 24 hours.
  
• Penalty of feeding on a creature:
  Regardless of whether the creature is newly dead or alive (unconsious or paralysed), these Attribute adjustments are applied:
  Personality -100, Intelligence -50, Willpower -50
  Agility +50, Endurance +50, Speed +50, Strength +50
  EDIT: Other than the Personality penalty, the others seem severe now.
  
• Penalties when feeding on the cold dead (after 15 in-game minutes since death):
  Vampirism stage 4 (blood-starved)
  All attributes a further -50
  Should I even make this available - in case players are not paying attention to the warning on the messages pop-ups?

I'd appreciate any criticisms, ideas or suggestions you guys would share.
Thanks!