This is what you currently have.
This is the intended modifications to the basic frame of the chair in order for it to fit in the costume. I forgot to put the spokes on the wheel, but they will still be there.
This is a basic sketch of the overall look of the finished costume. The goal is to sort of go for a bull-centaur look.
These were really quick sketches. I apologize for how bad I am at figure drawing. Tell me what you think?