The way I did it in LoG1 in the Wine Merchant's Basement was like this:
Before fall:
- Just before falling, increase the max health of all party members by 250 (250 was enough for my fall, you might need to add more)
- Heal the part by 250 health
- Open the trapdoor and start the falling!
Landing:
- Make sure they land on a pressure plate that triggers a script
- In the script reduce the max health and health that you added before (250 health in my case)
- Set the health of all party members to 1 (but not the max health), to make it seem like they're really lucky having survived and have to heal up first
The source of the Wine Merchant's Basement is available in the thread in my signature.
You might be able to do something like this with the functions getHealth() and getMaxHealth() and setHealth() and such on the champion component.
I can't try right now (i'm at work) but you might give it a try.