I've briefly looked over this thread and I have a couple of ideas... 1) Encase crates (as they are movable objects) inside one way shield barriers. The objects will freely bounce up and down but won't be forced any higher the the barrier itself. The fast movement of the crates will be dodgy to walk on, and the player won't likely be able to jump... But it should cause the damage you are requesting. 2)Custom powerups can specify shield limits. In Halo 3: You can always have Less shields than your maximum, but if you go higher than your set shields... your shields will decrease overtime back to your maximum. If you specify the maximum for your player to have No Shields, and you pick up a custom power up with normal shields, overtime your shields will go down. Now in Reach, I'm not sure if this is flipped.... When you have No Shields, and you pick up an Overshield, you receive a shield bar, and receive no shields (Indicating you can't go higher than your specified level) If you specifiy Normal Shields, and you pick up a Custom Powerup that takes off your shields perhaps it may degenerate. This however, wouldn't affect your health. 3)Figure out a way to glitch the Soft Kill Zones. I'm sure there might be a way to remove the text from the middle of the screen... I've found that placing inversed one way barriers above and inside each other, you can glitch where your spartan "appears" and actually resides in retrospect to the games engine. This is, however, highly unpredictable. Again, this wouldn't decrease your health, but would provide onscreen animation that your "dying" slowly until you do randomly die. Personally, I'd experiment with number 2 more than the others... Although I'm not sure how you'd implement it. Number 3 may not even be possible, I just remember finding out the glitchyness of one way barriers when trying to make them into an energy bridge. For Example, with correct spacing and merging two layers of dual one way barriers facing opposite directions, you can completely render them obsolete... Like Red shield doors if you will....
A sofkill in conjunction with upside down softkill barriers could be interesting. I like what that guy said about upping damage resistance and weapon damage and using tripmines. Would make traps more viable, but I get the idea you're after Nexn and I don't think it'd be possible. You're just gonna have to stick with the death pits.
I think the Hill thing is possible if you set the effects like Stevo did in his Custom Powerup effect above ^ Or, I think you can make your Sheild RECHARGE Rate in a hill to like, say -10%. That would seep away your health, I think.