What is the property of certain animations, such as power attacks that prevents actors/the player from moving while using them? Is it something that can be changed with the CK or part of the animation files themselves? If it's the latter, would it be possible to easily change that property for one of the game's animations using a tool like nifskope?

Behavior -> not alterable.... let it go. :/

Well that svcks. Hopefully someone will open it up in the future.