People like Kilkenny have been writing about 3rd parties for 200 years. It's a waste of energy. Unless you have 20 million people in it, and can prove it, It's far harder than anyone knows (and takes years). I think the goal should be to make the parties come back to serving the people. They are politicians. Show them the votes, and they will kiss your ass almost as fast as that of any tasty lobbyist.
Our mistake on the American left is always looking for magic bullets. There are none. Except the people themselves. Get enough people in the streets, and keep them there, and you won't need a 3rd party. You will have the sympathy and vote of the people. And there has always been strength in that. Our problem as a culture is not voting for change; it's thinking that our obligations end there.