I think the real goal regarding the horrors of "Old Noapte" is simply that the setting is maintained, and night time is IC'ly scary, but at the same time, players aren't punished for being out at night. I won't speak for anyone else, but I certainly log in hoping as a player that something scary is going to happen. So, there should be IC motivation for anyone in their right mind to go inside, but interesting situations to play through as players. Maybe not rewarding to where your character is out seeking it every night, but the player shouldn't feel like they're being driven away from the scariness, when that's what most if not all of us log in for.
Here's some ideas for DM's and MPC's to play with or off of, if they want.
1 - Play off of the themes that are already there. Have a vampire set up shop outside, looking like just another vendor. Next thing you know, people are getting charmed, led off to the Zeklos crypt, and drained, some to death. Take the time to develop monsters as characters who are out there often enough for long enough to actually seem like part of the normal social landscape. Do it in such a way as to make it look like PC's who are completely innocent are the actual culprit. Now not only do you face the danger of being drained for being out at night, but you also could be falsely accused of vampirism yourself!
2 - Recycle the above with rebel attacks, both in the potential of being victimized, and in the risk of being falsely accused.
3 - The wererat idea is a great one, stealing people's wares. Bring on a pack of them.
4 - Send the garda out during the day, asking around about individuals who were hanging around at night, because xyz happened, and everyone who was out there is wanted for questioning. And we all know what "questioning" means in the citadel.
5 - Use the vampiric charm ability to cause PC's to do things they normally would not do. One warrior picks a fight with another, and both fight to the death. Regardless of who wins, someone has died, and Old Night has claimed a victim.
The utmost of badness doesn't have to happen to everyone who runs afoul of "Old Night," and certainly not in huge swaths of the population who are out at night. With a little thought, scenarios could be created that are really cool for players to play through, but yet provide incentive for characters to go inside. I think what we're all looking for in gothic horror play is situations where the character says, "Oh no!" but as players, we can't wait for the next scene to happen.