Level Drain

One of the things in D&D that makes certain undead scary is level drain. These were neutered in 3.x and Pathfinder; instead you gain negative levels, which confer some nasty effects (-5 hit points, loss of spells, -1 to practically all rolls), but doesn't actually remove levels and allows a Fortitude save to recover from the effects a day later.

I'll have none of that. But how to convert the old level drain effect to GURPS, given that GURPS doesn't have levels?

As mentioned in this post, I'm using the conceit that 20 points is roughly equivalent to a level, starting at 150 points. Right now I'm doing this mostly for pacing (how many points should the PCs have if the average party level of an AD&D party would be X at this point?) but it could serve in this stead as well.

Now I'm stuck between three options:

1. Each hit from a level-draining monster drains 2 character points, period. Be careful.
2. Each critical hit from a level-draining monster drains 20 character points. They're dangerous, but you might survive if you need to go toe-to-toe with them.
3. Each hit from a level-draining monster drains 20 character points. Once a character gets to 0 character points, they're slain, no resurrection. If a character goes below 125 points, the player can choose to retire them.

I really don't know which one to pick? Which would you choose? In order to maintain that truly frightening level drain ability, should I go with #3? Am I just being too chicken?