The problem with a pure battery solution is that outages can last and last and last (as I'm sure some people are going to find out shortly)
The problem I see with bicycle generators is they're designed to put out quite a bit more power than you'd need for a sewing light so they would - except for the top notch systems - put a noticable drag on the treadle. I think I'll just make sure we always have a hand crank up and working.