You could potentially do something like that. However you'd have to setup a tag block in your scenario's py tag- Wait no scratch that, the py tag is closed source. You'd have to create your own scenario_trigger_volume_extension tag or something which has a tag block which takes the name of the trigger volume and a real value for it's gravity. Then you could just have an Update function check to see if the local player (this would only work for campaign) is in any of those, lets call them gravity well volumes, and then update the gravity to what that extension says.

you could end up with something like:
Code:
scenario_extensions
    * tag_block: scenario_gravity_well_block
        - tag_string: trigger volume name
        - word_flags: flags
            - use interpolation
        - short integer: interpolation speed (game ticks or something)
        - real: gravity f(x)
        - real_bounds: gravity interpolation range
If this was halo 2 or later, you'd have the benefit of a mapping_function to define a much more robust interpolation function.


For your second question: it's not implemented...please explore the source code.