I think the most promising interface is a parser with Threaded Conversations – an interface which isn’t limited only to conversations btw. It allows the author to give suggestions for the next turn, while allowing the player to type anything at all. It allows for unique actions without coding up verb after verb each for a single use. It would even be possible to have the suggestions be hyperlinks so that the players wouldn’t have to type unless they wanted to go beyond the suggested paths.
