Vampirism in a One-Shot

This situation keeps coming up at our weekly one-shot RPG group. Given lots of latitude on character concept in various scenarios and systems, people (including me) keep being drawn to Vampires.

Depending on the system (and I'm talking about some very rules-lite "hippy games" - Risus, InSpectres, Fudge/Fate, various homebrews, etc), being a Vampire could potentially be giving the PC a ton of power, but it's generally tempered by at least one very significant drawback - you're vulnerable during the day.

Of course, there's a problem there. Since we're doing one-shots, the last thing you want is for the players to squander time and dally and never get around to the plot. There's an out-of-character clock ticking, and the most common way to deal with that reality is to throw some challenge at the players that must be dealt with on an immediate (and unforgiving) time table.

Of course, that makes Vampirism all the trickier than it is normally. If your whole scenario must be dealt with in the next few in-character hours, the sunlight drawback gets either over- or under- emphasized. Either they never get to use their cool powers, or they never face the only source of real danger. This matters to me, because I plan on running some games (with this group) with fairly open character generation rules, and it seems likely to come up. It's probably less of an issue than I'm making it out to be, but it occupies my brain none-the-less.

There's several ways I can think of to deal with it:

• Don't let PCs be Vampires.
• Let it slide - set your game at night so they aren't restricted, and just not sweat the power they've gained.
  
• Make 'em pay - set your game in daylight so they're in constant danger or at reduced power.
• Do the Buffy thing - a heavy blanket, thin paint on the windows, or crappy blinds will protect you, but get thrown outside and you start burning.
• Lean on Vamps other weaknesses - set the game at night but introduce vampire hunters, garlic eaters, priests, running water, etc.
• Length of day: Prep every scenario so it takes roughly 24 hours in-character-time to resolve, or starts a couple hours before rise/set, and any potential Vamp will be at full-strength in some scenes but vulnerable in others.
• Scale back Vampirism: Disallow vampiric "bundling", and make them buy healing, shapeshift, hypnotism, etc as seperate powers. On the plus side, they won't get the drawbacks unless they want them too. (Though, I can't think of any games we've played where a PC would have that many powers/options if Vampirism weren't a semi-nebulous package deal.)
  

I'd love to hear some opinions on what you'd do in this situation. There's probably options I'm completely overlooking. Please let me know (in the comments) section what you'd be inclined to do.

Are there any options on that list that would piss you off if a GM did them in a game you were playing?