Is it possible to make completely custom cutscene animations, not with pre-recorded animations but with animation, like in the original game. I have a few really interesting ideas that will only work if I can make new animations for cutscenes and not prerecorded ones.

You can create animations in 3ds max, import them into halo and then run them on a biped.

(custom_animation biped where\the\animation\is animation_name 1)

http://hce.halomaps.org/index.cfm?fid=1326 ?idk just found this through google