I mean the problem with thirs parties is they are full of loons, but I can easily manage a somewhat credible Libertarian platform drawing from parties like the Free Democratic Party, the Lib Dems and the Icelandic Pirate Party. You would have to ouster the Ancaps, the racists, the paleos etc. though.
All of the American third parties are full of loons, but this is by design as they act more as activist social clubs than serious electoral vehicles. Look at what happened with the Florida Libertarian Party over Augustus Sol Invictus, a pagan fascist who managed to coopt the statewide party with little effort. The Green Party is basically the same, except with truthers and trots instead of neo-confederates and objectivists. Any attempt to reform these parties will be resisted viciously, as their supporters don't really care about winning or expect to win.
