You know how in the later Halo games, I think it might just be Halo 4, how where you jump down a gravity lift room, it initially carries you, and then you descent is slowed just enough that you land on the ground safely? Is it possible to script something like this, or does it have to be an animation?

It depends if your lift is in a closed space or not.
If your lift is in a closed room (like the High Charity lifts in Halo 2) then you would just need an animation: you make a lift animation for a box (with a marker that moves with it) and you make a script that, once you pass through a trigger volume, starts the animation and attachs the player to the marker, in order to not make him move while ascending. Once the animation is finished, you can detach the player.
If your lift is in an open space, then I guess you should use damage_effects, but don't expect big results. Honestly I'd prefer using lifts only in places where they are needed (like the closed spaces) in order to use the first method.