The idea is interesting, but I would imagine you need to take into account various forms in which people might want to express their intent. For example, "train from A to B" instead of "I need a train from A to B", or "flight tickets to C" (the current location omitted and can be detected using IP geolocation).

Another thought I had was that many people might actually prefer to interact with checkboxes and select from a list, especially if they're using a mobile device.