i don't know about the insurance, we always do it outside, but there are a lot of fire spinners in Atlanta, myself included, and nothing seems to "spark" a happy spectical than a taste of fire.
another thought, stilt walkers are a crowd pleaser, both the tradititonal stilts and the more recent jump stilts. i'm learning those right now, maybe i'll be able to do a stilt/spinning combo act. That'd be awsome!
Hope that helps give you ideas.