However, such a controller would require enormous complexity to allow for all possible scenarios. If this controller were unable to encapsulate all the contexts, it would need to adapt every time the context of the movement changed before it could produce approximate motor commands - this would produce transient and possibly large performance errors.

I've heard it said that when someone slips on a banana, the humor is closely connected to the way that normal walking movement continues into an inappropriate context. That sounds to me like a large performance error, and a brain is certainly complex.